In the latest attack, police say a 31-year-old woman was followed into a building on East End Avenue just after 1 a.m. Wednesday.
The suspect grabbed the woman's buttocks and then fled the scene.
He was described as a Hispanic man, about 5-foot-8 with medium length hair, wearing yellow shorts.
Police believe the same attacker has struck at least six times in the past month and a half. They are working on a sketch of the suspect.