The ratio of males to females was 11.2 to 1. Sixty-four percent were homosexual or bisexual men, 18 percent were intravenous drug abusers, and 7 percent were both. Heterosexual transmission was presumed responsible for AIDS in 2,189 patients. Twenty-six percent of AIDS patients were black and 14 percent Hispanic. Twenty-two percent of the AIDS patients lived in New York City and 27 percent in the western United States. Surveys of the prevalence of HIV antibodies have shown it to be 20 percent to 50 percent in homosexual men, 70 percent in persons with hemophilia A, 35 percent in those with hemophilia B, 5 percent in intravenous drug abusers nationwide, and 50 to 60 percent in intravenous drug abusers in New York City. Tables and 3 references.