The primary objective of this study was to identify the social, psychological, and behavioral factors that influenced recruitment in AIDS clinical trials. The study compared HIV-infected individuals participating in a trial (n = 113) and a group of HIV-infected patients not currently participating in a trial (n = 103). Trial participants were more likely to be White (61.5% vs. 38.8%, p < .004),="" msm="" (40.7%="" vs.="" 20.4%,="">p < .0001),="" with="" no="" idu="" history="" (74.0%="" vs.="" 38.8%,="">p < .0001).="" among="" trial="" nonparticipants,="" 42.2%="" indicated="" willingness="" to="" participate="" in="" a="" trial.="" gender,="" race,="" and="" idu="" history="" was="" not="" related="" to="" willingness="" to="" participate="" in="" a="" trial.="" trial="" nonparticipants="" rated="" almost="" all="" aspects="" of="" the="" trial="" regimen="" as="" significantly="" more="" difficult="" compared="" to="" trial="" participants.="" trial="" participants="" differed="" significantly="" on="" sociodemographic="" dimensions="" and="" in="" beliefs="" and="" attitudes="" toward="" medical="" therapies.="" these="" differences="" may="" limit="" the="" generalizability="" of="" trial="" results="" and,="" consequently,="" the="" effectiveness="" of="" hiv="">