Child abduction by strangers, the experts continue to say, is not a growing menace. The number of cases -- 115 or so a year, according to the most recent federal statistics -- has remained steady. Yet, the crime has been prominent this summer because of a few startling cases.

In one, Elizabeth Smart, 14, was reportedly led from her bedroom in Salt Lake City on June 5 and has not been found. On July 15, Samantha Runnion, 5, was pulled screaming from a courtyard near her town home in Stanton, Calif., and abused and murdered. Two 10-year-old friends in Soham, England, disappeared on Aug. 4 and were found dead in the woods two weeks later. Similar atrocities have occurred in recent months in Missouri, Texas, Virginia, Oregon and Wisconsin.

What kind of person does such a thing?

After studying hundreds of cases, scientists can provide at least a partial answer. The broad population of child molesters, most of whom do not abduct their victims, is too diverse to fit a single psychological profile, but the far smaller group of those who abduct and keep children for sexual abuse share common traits.

At least 95 percent are men, and they tend to be unmarried and have few friends.

''In general, as everyone suspects, these people are losers,'' said Kenneth V. Lanning, a retired Federal Bureau of Investigations agent in Manassas, Va., who is a consultant for the National Center for Missing and Exploited Children.