OBJECTIVE To describe clients, operation and impact of an African public HIV testing and counselling centre. DESIGN AND SETTING Analysis of samples from clients attending the AIDS Information Centre (AIC) in Kampala, Uganda in early 1991. SUBJECTS HIV-1-positive and HIV-negative consecutive clients (250 of each), 86 consecutive couples, and 200 consecutive clients who were HIV-negative in 1990 and were attending for their repeat test. MAIN OUTCOME MEASURES HIV seroprevalence rates, attitudes, behaviour and behaviour change. RESULTS HIV-1 prevalence was 28% overall, 24% in men and 35% in women. Reasons for taking the HIV test were a planned marriage or a new relationship (27%; 84% in couples), to plan for the future (35%), distrust of sexual partner (14%) and illness or disease/death (not HIV-specific) of partner (20%). The majority of the reported intentions in response to a positive or a negative HIV test result were positive, demonstrating the ability to cope with this information. Of repeat clients, two (1%) had become HIV-1-positive. The majority of repeat clients reported one sexual partner only (67%) or sexual abstinence (25%). Compared with pre-test information from AIC clients attending for the first time, repeat clients reported casual sexual contacts less often (6 versus 25%) and, of those, the majority used condoms. CONCLUSIONS Our study demonstrates the demand for and the feasibility of confidential HIV testing and counseling services in Uganda, and illustrates the value of these services in achieving behaviour changes. Such services should be considered an additional approach for the reduction of HIV transmission in Africa, especially in areas with high HIV seroprevalence rates.