A total of 26,210 serum samples from 16 acquired immunodeficiency syndrome (AIDS) risk groups were tested for human immunodeficiency virus (HIV) antibody, using mainly enzyme-linked immunosorbent assay (ELISA) and Western blot. Among 751 homosexuals, 15 were positive (2.0%): 3 were full-blown AIDS patients; 2, AIDS-related complex (ARC); 1, "possible" AIDS; 1, persistent generalized lymphadenopathy (PGL); 5 were asymptomatic carriers and 3 refused to be interviewed. Among 171 hemophiliacs, 29 were positive (17.0%), of whom 1 and only one developed full-blown AIDS. One asymptomatic homosexual HIV carrier had donated four bags of blood which resulted in a seropositive uremic patient who currently has no AIDS-related symptoms. In general, antibody titers were higher in asymptomatic HIV-carriers, PGL and ARC than titers in those of patients with full-blown AIDS. Among the low-risk groups, two seropositives were encountered: one was a patient with chronic oral candidiasis, the other was a transvestite. Neither of these two patients had any high-risk factor. They yielded strong ELISA and only one p24 band on Western blot. The possibility of obtaining false positive tests when using Western blot should be strongly considered. The conclusion is that AIDS has invaded Taiwan, but the prevalence of the HIV infection is presently low. Presently and importantly, active community efforts are needed to minimize HIV transmission.