Dolores Little was at home in her Hyattsville apartment one afternoon last fall when 14-year-old Desmond, the youngest of her three teen-aged sons, "came busting through the door, all upset, saying, 'Mama, a man just grabbed my friend and he was trying to rape him.' "

"He was really upset by it," recalled Little, who since then has not let her sons play outside alone or leave the apartment after dark. "He didn't want to go to school."

The incident was the first time that Little had heard of a series of sexual assaults on eight boys near Prince George's Plaza in Hyattsville that police say began in July 1982.

News of those assaults, and of an apparently unrelated series of nine attacks on at least 10 girls and women near West Lanham Hills and the New Carrollton Metro station since March 1983, has been released by Prince George's County police only in recent weeks.

"Why is it nobody's saying anything?" asked Little, a District employe who said that the incidents have prompted her to search for a new apartment. "Why is it such a hush-hush thing?"

While sexual assaults "are hard on the families," she said, police "should have come out and told people what was going on."

Police have said that they often are reluctant to release news of crimes for fear of inciting "copycat" criminals or slowing progress in their investigations by driving the offenders "underground" or to a different location. But department spokesman Bruce Gentile said that police decided early this year to publicize the assaults on television "Crime Solvers" programs after they ran out of leads. They released two composite drawings of men, one the suspect in the assaults on the boys and the other believed to have been responsible for the attacks on the women.

Police said they are convinced that one man is responsible in each series of attacks, because each set of victims has given similar descriptions.

Most of the Hyattsville attacks were on boys between the ages of 12 and 15 and took place in late afternoon as the victims were walking from Northwestern High School or Nicholas Orem Middle School.

Five of the assaults occurred in a large wooded field behind the high school that is crisscrossed by a number of footpaths leading to several large complexes of tidy brick garden apartments. The most recent assault was reported Jan. 24.

Police have shown principals at the schools composite photographs of a suspect, according to Gentile.

Peter Blauvelt, director of security for the county school system, said no special safety programs are planned in the schools. But Toni Menchan, principal at Nicholas Orem Junior High School, said she warns students over the public address system to "never walk alone, not after school or on weekends, either." She said a group of parents now watches the students walk home after school, but without the students' knowledge.

"We figured they were frightened enough anyway," Menchan said.

The other series of assaults, the most recent of which was on Feb. 24, ranges over a wider, largely commercial area between Landover and New Carrollton and has involved 10 girls and women between the ages of 11 and 27. Many of the attacks, mostly in the early morning or after dark, involved women walking to or from the New Carrollton Metro station or from stores in the commercial area.

Gentile said that police have sought FBI help in constructing a psychological profile of the suspect in the attacks on females and are considering doing the same thing in the male assaults.

He noted that in both cases there was a year-long gap between the first and second incidents, leading police to wonder whether the attackers had been jailed in the interim.

News of the assaults has spread fear in both communities.

Nina McNeal, who lives near Northwestern High School, is to meet with county police today to discuss starting a Neighborhood Watch program.

"My 12-year-old's friend was raped, and that was a little close to home," said McNeal, who lives in the Highview Apartments, which border the wooded area where the attacks have taken place.

Police have put up several posters bearing a composite sketch of the man who has attacked the boys, but McNeal said that the picture "is not much of a deterrent."

At the New Carrollton Metro stop, Roderica Curtis, who commutes to her job at Riggs National Bank downtown, said that she has stopped using a pathway through a wooded area near the Metro to reach her home on Riverdale Road in New Carrollton.

Since learning about the rapes, Curtis said, she has started taking the bus to and from the Metro, even though it takes twice as long as walking home.

"It really scared me," said Curtis. "It could have been me."

Added Sarah Murphy, of Lanham, "My daughter's telling me to be careful and I'm telling her to be careful."

Some lives have been affected more directly.

One woman, a 31-year-old Hyattsville resident, was at home Dec. 19 when a friend of her 14-year-old son pounded on the apartment door, telling her to call the police. Just as officers arrived, her son emerged from the woods, wearing only his underwear.

"What do you say to a child who's just been raped?" asked the woman, who had moved to the Washington area in September. "I said, 'I love you, I'm sorry this happened to you, you were just at the wrong place at the wrong time.' "

The youth had nightmares and refused to return to school after the attack.

"He was incapable emotionally of staying here," his mother said, so she and her husband sent him out of the country to stay with relatives.

"I was surprised that two teen-aged boys would be attacked," she said. "I just assumed they were safe."

Investigators said that the victim of the latest attack ran away from home and now lives with relatives in the Midwest.

Some residents remain unaware of the incidents.

"Rapes? People are getting raped?" asked Rosa Johnson, a cashier at the New Carrollton Metro parking lot.

"There's still a lot of people that live here that don't know about it," said McNeal.

In the case of the attacks against boys, some have suggested that the homosexual nature of the incidents has contributed to the slow spread of information about them.

"The families don't want the stigma attached to homosexuality to become public," said spokesman Gentile.

The attacks are "a very touchy subject," said Michael Ivey, the resident manager of one of the apartment complexes near Northwestern High School. "We don't want the community to panic."