Carlton L. Bittenbender's references had been checked, and he had come up clean.

Those who hired him nearly two years ago as leader of Reston's Boy Scout Troop 1970 telephoned his references and sent his name to Boy Scouts of America headquarters, where a computer lists 2,000 former Boy Scout leaders with previous arrests, convictions or problems ranging from alcoholism to inability to manage funds.

But in August, several months after resigning as scoutmaster, Bittenbender was arrested by Fairfax County police and charged with aggravated sexual assault and sodomy. He since has been charged with three additional counts of sex abuse to juveniles.

And police in Barrington, R.I., where Bittenbender was a scoutmaster until 1981, said he had pleaded no contest to four similar charges there and had received a five-year suspended sentence.

"For some reason, the screening process didn't work," said Robert Wesson, chairman of the committee that hired Bittenbender. "As a parent, I felt quite betrayed by these circumstances . . . . "

Wesson's concern is shared by others in the Boy Scouts and in groups nationwide that recruit volunteers to work with children. Alarmed by a spate of recent arrests for child sex abuse in the Washington region, leaders of those groups are seeking ways to halt such incidents -- from tougher screening procedures to guidelines that discourage individual coaching on county athletic teams.

Big Brothers of the National Capital Area, an organization that matches men with young boys to provide father figures for orphans and boys from single-parent homes, prides itself on a tough screening process that requires four references, an employment history and a waiver signed by each applicant allowing access to his police records.

But in light of recent sex abuse cases in this area, "we have to check everyone even more carefully," said caseworker Ron DuBrey.

"We're reviewing all the processes we use for screening applicants," said Connie McAdam, recreation division chief in Arlington.

Montgomery County recreation directors, who accept more than 1,000 volunteers each year to coach athletic teams and lead other youth activities, in May began checking police records of applicants for paid part-time work as playground leaders or summer camp directors. While they have no plans to conduct police checks , they are considering other ways to curb opportunities for sexual abuse, such as discouraging individual coaching.

"With a lot of these sports, there is a natural tendency to want to give individualized instruction," said David Robbins, Montgomery County director of recreation. "We ought to try to discourage that."

For many organizations, tougher screening is a sensitive issue: leaders want to protect children from abusers without scaring off sorely needed volunteers.

"We've always had difficulty getting enough volunteers to work with the youth sports program," Robbins said.

"When somebody arrives on the scene who is willing to do the job, you're hard pressed to say no," said Judy Etheredge, whose 11-year-old son was in Bittenbender's troop.

Since Bittenbender's arrest, she has urged Boy Scout officials to adopt stricter screening methods.

"We want the Boy Scouts of America to look at their procedures carefully and see what they can do to tighten things up . . . . They have to do something about their screening process that puts these people on the spot," Etheredge said.

Since the early 1900s the Boy Scouts have kept a list of people who "for one reason or another, do not fit our standards of leadership," said Barclay Bollas, national news editor for BSA headquarters in Texas. The confidential list is supposed to prevent former troop leaders with arrest records, drug addictions or other problems from registering as scout leaders elsewhere in the country.

Bittenbender's name never reached the national list, said Vincent Borrelli, a Boy Scout executive for the Narraganset Council in Rhode Island.

"I can't answer why his name wasn't forwarded to the national office," Borelli said. "For some reason, it was not done. It may have been just a mistake."

Even when names are properly forwarded, the list has its limits, Bollas explained, because it includes only persons previously involved with the Scouts.

"It's not a catchall," he said. "Obviously, you're going to have some problem people still slip through. But we haven't been able to come up with a better system."

Even the most scrupulous examination of police records could fail to identify a potential child abuser, say area detectives, because many people arrested on such charges are first-time offenders.

In one such case last week, the Arlington County School Board fired Charles P. Whalen, a Wakefield High School teacher's aide and Arlington Boy Scout leader, after he was charged with aggravated sexual battery of a juvenile. Whalen, 37, had worked for the schools since 1977.

Ultimately, officials say, volunteer organizations must rely on thorough interviews, references and the perceptiveness of staff members and parents -- a human gauge that admittedly is flawed.

"There is no perfect pitch when it comes to human nature," said Borrelli of the Rhode Island Boy Scouts.

Wesson noted that Bittenbender was liked by parents and trusted by Scouts, and said: "He is a very up-front kind of person, enthusiastic. He really gained the trust not only of boys in our Scout troop, who thought he was super, but of the adults."

According to local police officers, those in the best position to notice a child's uneasiness about a coach or youth group leader -- the child's parents -- often are the most reluctant to broach the topic.

Sexual abuse "is the last thing they want to discuss, and we're the last ones they want to discuss it with," said Detective Michael Kyle of the Arlington police.

Since most agree that there is no foolproof method for recognizing potential child abusers, parents must be especially watchful for signs that such abuse has occurred, said Etheredge.

"Parents must be tuned in to the fact that the very people you teach your children to trust can't always be trusted," she said. "You don't have to suspect everyone [of child abuse], but you have to be aware that it can happen anywhere."