To compare survival of patients infected with HIV-1 and HIV-2. Longitudinal follow-up of 175 HIV-1- and 294 HIV-2-infected patients identified in, or referred to a hospital in The Gambia. Survival analysis methods were used and the death rate ratios for HIV-2 relative to HIV-1 patients were estimated using proportional hazard regression models that allowed for age, sex and clinical or immunological features. The overall death rate ratio for HIV-2 relative to HIV-1 was 0.67 [95% confidence interval (CI), 0.49-0.91] when adjusted for age, sex and World Health Organization Bangui clinical classification. When allowing for age, sex and three strata of CD4+ count, the rate ratio was 0.64 (95% CI, 0.43-0.94), and for three strata of beta 2-microglobulin levels 0.60 (95% CI, 0.42-0.84). Mortality rate in HIV-2-infected patients is approximately two-thirds of that for HIV-1-infected patients.