In a community study, the HIV-1 and HIV-2 antibody status of the inhabitants of 100 randomly chosen houses in Bissau, West Africa, were followed from 1987 to 1989. There was no HIV-1 infection alone, while the HIV-2 seroprevalence in adults was 8.9%(58 of 652) in 1987 and 10.1%(61 of 603) in 1989. HIV-2 seroprevalence in 15− to 39-year-olds was 6.1% in 1987 and 11.3% in newcomers in 1989 [the Mantel-Haentzel weighted relative risk (RR MH)= 1.86; 95% confidence interval (CI): 1.07–3.24]. Three hundred thirty adults who were HIV-2 seronegative in 1987 were reexamined in 1989; seven had seroconverted. Follow-up time was 700 person years, giving an incidence of HIV-2 infection of 1 per 100 person years. With a history of sexually transmitted disease (STD), the RR of seroconverting was 9.95 (2.31–42.80). Blood transfusions received since 1987 did not result in seroconversions. No case of vertical transmission of HIV-2 was seen. There was an excess mortality in those who were HIV-2 seropositive; however, it was statistically significant only for children (RR= 22.27; 95% Cl: 6.92–71.70; p< 0.0001), not for adults (RR= 2.16; 95% CI: 0.81–5.76; p= 0.23), when considering death from disease only.