Detectives say this man followed a woman from 170th Street and the Grand Concourse to her apartment around 5 Saturday morning.
He then sexually assaulted her in the building lobby and ran away.
The suspect is described as a black man in his 20's, approx. 6'0" in height, 170lbs, with black hair(Shoulder length dreadlocks) and brown eyes.
He was last seen wearing a gray hooded sweatshirt, gray pants and a gray baseball hat.
Anyone with information in regards to this incident is asked to call Crime stoppers at 1-800-577-TIPS (8477).