This paper describes the sociodemographic characteristics of people who donated blood to the New York Blood Center between April 1985 and February 1988 and tested positive for antibodies to HIV. Information on HIV-related risk factors and knowledge of blood screening is presented for seropositive donors who participated in an evaluation study. The most commonly reported risk factor among men was sexual contact with another man, and many of the male seropositive donors reported sex with an intravenous (IV) drug user or use of IV drugs. The proportion of men reporting sexual contact with another man decreased over the period of the study, and the proportion reporting use of IV drugs or sex with an IV drug user increased. Awareness of blood screening for HIV antibodies increased over the study period. The greatest increase was among those donating for transfusion, but only about a quarter of seropositive donors used the confidential unit exclusion (CUE) process.