In bivariate analyses, undetectable and on-PrEP men had been to more sex parties in the prior six months, had more anal sex partners there, and had higher rates of sexually transmitted infection (STI) diagnoses than men never on PrEP. We compared responses from HIV-positive-undetectable men (n = 36), HIV-negative men on pre-exposure prophylaxis (PrEP n = 62), and HIV-negative men never on PrEP (n = 113). We conducted an online survey with 211 New York City MSM who attended sex parties in the prior year and asked them to describe their behaviors and perceptions of risk. Men who have sex with men (MSM) who attend group-sex events often engage in risky sexual behaviors that contribute to the high human immunodeficiency virus (HIV) incidence among this population.
