The body of a slightly retarded 21-year-old black man was found in an abandoned apartment building here today -- the 23rd official victim in the string of murdered and missing black youths that has haunted this city for almost two years.

The latest victim was identified as Larry Rogers, who disappeared from outside his northwest Atlanta home March 30 and was reported missing three days later. Medical examiners have not yet determined the cause of death, but Public Safety Commissioner Lee Partick Brown told an afternoon news conference "we will carry the case a as homicide."

Rogers -- a slim young man with the face of a teen-ager who eagerly sought odd jobs in his neighborhood -- is the second mentally retarded black youth found murdered here in the last two weeks. The body of Eddie Duncan, 21, was found floating in the Chattahoochee River March 31, two miles from where the body of 13-year-old Timothy Hill was pulled from the river the day before.

Rogers' foster father, George W. Hood, 79, waited three days to report his missing because, he said, he "didn't want to make a false alarm."

Hood, a semi-retired barber, and his wife raised Rogers as one of five foster children. Rogers, afflicted with a speech impediment and learning disabilities, was baby-faced, undersized for his age and slow to learn. But teachers promoted him "because they just got tired of fooling with him," said Hood.

The young man dropped out of high school, briefly signed up for state vocational training and special education classes, then took to earning spending money which he used to buy a stylish wardrobe.

The day Rogers disappeared, a neighbor told police she saw him sitting "stiffly" and staring straight ahead in a faded green 1966 Chevrolet station wagon. Behind the wheel, she said, sat a light-skinned black man, about 50, with a thick, "false-looking" mustache and eyelashes, and long, stringy, gray-and-black hair.

The task force adopted the cases of Rogers and Duncan because both were considered child-like and vulnerable, and because their street-wise lifestyles closely paralleled those of some of the other victims.

Moreover, Duncan and two of the other victims were found wearing only undershorts. Police said Rogers had on undershorts and gym shorts pulled down over his buttocks.

Medical examiners have been unable to find conclusive evidence of sexual abuse, but have not ruled out a sexual motive in the cases.

Rogers lived about two miles from the site where his body was found -- a dead-end street in the shadows of downtown Atlanta's skyline of glass and steel. Dozens of federal, state and local police officers, reporters and neighbors swarmed to the scene today.

Melvin Jackson, 33, a floor installer who sometimes played basketball with Rogers, came on his lunch hour. Wednesday night, he said, he turned on his television and saw the composite drawing. It resembled a man he had seen cruising the neighborhood twice before Rogers disappeared, once in a gray or green car and the second time in a brown van, he said.

Police have been investigating sightings of vans and green cars in several of the cases, and took special interest in a 1968 four-door Buick found parked, stripped of its tires and propped on cinderblocks beside the boarded-up brick building where Rogers' body was found.

But Commissioner Brown said police had found no connection between the homicide and the car, reported stolen recently.

A call from a resident who was angry over the abandoned car, reportedly seen cruising the neighborhood, brought a patrolman to the end of Temple Street NW at 11:30 a.m. to day.The officer smelled an odor coming from a nearby apartment. When he investigated it, he found the body.