THE NIGHTMARES HAVE returned. After four years of psychotherapy, 29-year-old Amy thought the past was behind her. But in her dreams, she is 11 years old again, back when her ordeal began, lying in bed with her stepfather. What begins as fondling turns into something else. For seven years she had suffered from his sexual advances, frightened, confused by her mother's silent complicity. Then Amy realized that her sister, herself just turning 11, would be his next prey and contemplated reporting him to the authorities.

Linda seems to be a well-adjusted extrovert, on her way to a doctorate in clinical social work. In fact, she finds most men sexually repellent, particularly those in the age group of the uncle who sexually molested her some 17 years ago. Like many such victims, Linda jumped into an early marriage in a vain attempt to resolve her feelings of loneliness and sexual inadequacy; the marriage lasted 18 months.

Last year, when Joey was 8 years old, he was raped by the 13-year-old nephew of his mother's boyfriend, Joey couldn't bring himself to tell his mother. In the months that followed, he became afflicted by nervous tics and a fear of the dark, and he suddenly developed an aversion to school.

"Sexual abuse of children is a crime that our society abhors in the abstract but tolerates in reality," says Dr. Suzanne M. Sgroi, former chairman of the Sexual Trauma Treatment Program in Hartford, Conn. "It seems to be 'too dirty,' 'too Freudian' or perhaps 'too close to home.'"

Too close, indeed. The standard image of the child molester as a lurking stranger has been banished by recent studies. Most victims are abused over an extended period by someone they know and trust, someone they are often physically and emotionally dependent upon -- a parent, another family member, a babysitter, neighbor, teacher or playmate. The incidence of the experience is also far greater than previously thought. According to a 1979 survey of college students, 20 percent of the women and 10 percent of the men said they had been sexually victimized as children without reporting the incidents.

Moreover, all evidence suggests that the likelihood of victimization is the same for the child of a suburban corporation executive as for the inner-city child of an unemployed laborer.

What is clear is that taboos have kept the public -- and the medical and legal professions as well -- from focusing on the subject. But in recent years, the advent of the women's movement and society's increasing sophistication about sexual issues have led to dramatic change. The increased reporting of the crime, according to experts, has been explosive. Hundreds of treatment programs have sprung up for victims (and a few for abusers as well). Some public schools are experimenting with efforts to educate students about the subject. For the first time federal funds have been voted specifically for this problem. However, there has been no significant change in the criminal justice system in which the protection of the victim is minimal and the likelihood of conviction and punishment of the offender is remote.

In the District of Columbia, for example, in the past two years a total of 411 sexual abuse cases that began at Children's Hospital's National Medical Center for the Child Sexual Assault Victim Assistance Project, (CSAVAP) have produced only 55 convictions with 47 still pending investigation and trial.

As David Finkelhor reports in "Sexually Victimized Children," a survey of 800 New England college students who had been sexually abused showed that 63 percent of the girls and 73 percent of the boys had not told anyone of the experience.

For one thing, children may not realize that they've been exploited. But there are other reasons. Carl Rogers is the project director of research and evaluation at Children's Hospital CSAVAP. He says that children don't tell because they're afraid of being punished or blamed, because they've been threatened or bribed -- and because they fear that no one will believe them.

Moreover, professionals acknowledge that not a single treatment program in the country today can guarantee that if an individual confesses, he or she won't be punished. "As a result, there are now thousands and thousands of children and families that won't come forward because they are terrified; they don't want to be responsible for a person going to jail," says Kee MacFarlane, program specialist for the National Center on Child Abuse and Neglect (NCCAN).

Even when children do tell an adult, sometimes they simply are not believed. Experts in the field reserve their harshest criticism for professionals who fail to recognize or report cases.

In a case in Troy, N.Y., for instance, a pediatrician diagnosed a clear symptom of child sexual abuse -- a 6-year-old patient's enlarged vagina -- as the result of antibiotics he had prescribed. He was not alone. The medical profession is responsible for only 12 percent of all reports of child abuse nationwide, according to a 1978 American Humane Association study.

When an instance of child sexual abuse finally does come to light, it is the victim who usually reports it. Sometimes, the announcement is very direct and convincing. Says Lucy Berliner of the Sexual Assault Center at the Harborview Medical Center in Seattle, "When a 6-year-old kid tells you that her dad is coming into her bedroom and asking her to perform fellatio -- even when there's no physical evidence, infection, no injury, no witness -- it's almost a prima facie case." On the other hand, a victim may offer subtle clues in conversation or in the form of drawings or play with dolls in the presence of a trusted adult.

Many young victims develop immediate physiological symptoms. They may suddenly have trouble sleeping or lose their appetite. They may become irritable, stage inexplicable temper tantrums, wet their beds. They may start to masturbate in public.

But child sexual abuse is also described by experts as "a psychological time bomb." The confusion, fear and sense of powerlessness it produces may not emerge until years after the event. This may explode in such self-destructive behavior as promiscuity, alcoholism, drug abuse, self-mutilation, and even abuse of one's own children, breeding a vicious cycle.

Regina Berg sits at her desk in the playroom at Washington's Children's Hospital. Facing her is an unprepossessing blonde woman whose strikingly pretty and demure 6-year-old intently plays with a doll on the carpet, seemingly oblivious to what is being said about her. Cheri's mother (the names of all children have been changed in this article) says, "I've always told her that if any boy, girl or grownup takes off your underwear, to tell me." Last month a 160-pound, 11-year-old male playmate apparently had sex with Cheri in a hall closet.

One of two programs of its kind in the country, the Child Sexual Abuse Victim Assistance Project at Children's Hospital was established in 1977 as a national pilot project. Since receiving its initial grant from the Law Enforcement Assistance Administration, Department of Justice, the project has served 500 children, most of them from the inner city; last year the caseload surged 70 percent.

Nearly half of the patients come to the project within two days of the disclosure of an incident, and a similar percentage of the cases involve parents, guardians or family members. A battery of initial crisis counseling, medical and legal evaluations and court preparation services are provided, but the process can be painfully slow. Although the project has a team of 10 medical, legal and social service specialists, only six work directly with patients. Treatment is short-term, averaging about two to three months per case.

Jenny, a 5-year-old girl in pigtails wearing a jean skirt, big black boots and a broad smile, enters the special playroom at the hospital and immediately heads for the dollhouse.

Susan Neal, a team member, directs Jenny to reenact what happened with her 13-year-old uncle. "We went upstairs," she says, "and played with my toys and he did a nasty." She demonstrates by putting one girl doll on top of another. Later, a medical examination will show that Jenny has contracted gonorrhea, as had her two sisters, also assaulted by their uncle, who is now up for trial.

Play therapy is used to test for emotional trauma, to gather information about the child's home life and -- as in Jenny's case -- to document culpability so that the offender can be prevented from repeating the offense. The work with the criminal justice system can be a frustrating experience for the project's team.

Legal advocate David Lloyd offers emotional support to victims and their families and coaches them for court appearances by playing courtroom roles -- a probing defense attorney, for example, or a hostile witness. He also helps to expedite the paperwork by establishing communications among the police, defense attorneys and prosecutors.

Tracy, 3, and Mary, 6, were allegedly raped by their mother's 34-year-old boyfriend, Johnny, while she was at work. Since the incident, both sisters have suffered from depression and nightmares despite heavy dosages of anti-depressants; they were out of school for more than a month. After Mary was given a gynecological examination, she asked: "What do I get for this?" Their mother then initiated legal proceedings against Johnny and placed the girls in the custody of a foster care facility until the crisis was resolved. Often, it is a year or more before a case is closed. t

Tracy and Mary were unusually fortunate. The police conducted an investigation charging Johnny with three counts of rape and two counts of "indecent liberties." The trial was scheduled three months later. Although Johnny's court-appointed attorney tried to establish that the children were too young to testify, to challenge their credibility, and to look for inconsistencies in their stories, the evidence was overwhelming in their favor. Johnny pleaded guilty to one count of "indecent liberties" and was given a 2- to 6-year suspended sentence, with a 3-year probation period, in which he was required to seek psychiatric treatment.

The girls did not have to testify in court, but had to repeat their story to several strangers. Most states, including the District of Columbia, require children to undergo a competency interrogation in which they are often asked such existential, difficult-to-answer questions as: "Do you know the difference between telling the truth and telling a lie? What is truth?"

Court records show that child molesters are rarely convicted, particularly in cases involving infants. "Nine times out of 10," says David Lloyd, "a crime done to a child under 6 years of age will probably end up with the offender getting away with it because the child will be deemed incompetent to testify."

The laws covering child sex abuse are fuzzy: all 50 states and the District of Columbia prohibit adult sexual interaction with children, for example, but there is no uniform definition of child sexual abuse. Laws vary from state to state. In one state, for instance, an incestuous father may be given no more punishment than an order to seek psychiatric treatment; in a neighboring state, he may be charged with a criminal felony and face a stiff jail sentence. In Florida a man convicted of incest has been given a life sentence; an incestuous father in Tennessee has been given a 3-year suspended sentence while the mother, in a separate trial, was jailed for 10 years for complicity.

Currently, there is no way of telling whether treatment rather than a jail term won't result in the offense being repeated. "From what we have learned so far, there appears to be a type of family and offender who can be helped and will change their behavior without the authority of the court," notes Kee MacFarlane of NCCAN. "On the other hand, some families and individuals won't change without all the clout that can be mustered on the part of the criminal justice system. The problem is for treatment programs to be able to demonstrate that offenders can be helped without incarceration."

Child molesters are not all men, but very little is known about the women offenders. Males who have been sexually assaulted by women are reluctant to report such victimization, experts say, because they are reportedly either afraid that they won't be believed or that their complaints will be thought foolish.

Like a courtship, an instance of child sexual abuse is a gradual affair as the child comes to trust and to feel a rapport with the adult. The offer of some kind of reward, such as candy or money, frequently eases the change from affectionate touching to masturbation and sex play. Or the child's need for attention and approval may be enough to lure him or her into a sexual liaison.

In 1974, Congress enacted the Child Abuse Prevention and Treatment Act. The National Center on Child Abuse and Neglect (NCCAN), an $18.9 million agency, was established within the Department of Health, Education and Welfare (now the Department of Health and Human Services).

The push to get funding for child sexual abuse treatment programs has begun but with little momentum. When Congress held its well publicized hearins on the sexual exploitation of children in 1978, "kiddie porn" and child prostitution grabbed all the headlines. Despite the approval of a four-year, $14.5-million authorization for child sexual abuse prevention, treatment, training, and research programs, no funds were appropriated for the first two years. Ironically, the only five projects supported by NCCAN in 1978 were the recipients of $500,000 diverted from programs intended for battered and neglected children.

The first grants are just now being awarded by NCCAN, which means the programs will be launched less than a year before the authorization expires. The entire issue could become moot if NCCAN, which will be subjected to a reauthorization of its own in 1981, is disbanded by Congress.

In fact the CSAVAP at Children's Hospital itself faces demise. Its funding is only certain until January 1981.

But by and large a long record of lukewarm support for child sexual abuse programs by the administration has apparently ended. Health and Human Services Secretary Patricia Harris is on record in support of funds for the treatment of child sex abuse.

"The Department is committed to seeing that NCCAN continues and this secretary has a greater commitment to child abuse and its resolution than any secretary has had in the past," says Ann Cohn, special assistant to Secretary Harris.