Summary:This study examines the prevalence and risk factors for Human Immunodeficiency Virus type 1 (HIV-1) and type 2 (HIV-2) infection in pregnant women in Dakar, Senegal. From April 1991 to January 1993, 9,518 pregnant women were interviewed and serologically tested for antibodies to HIV-1 and HIV-2; 26 (0.3%) were HIV-1 seropositive, 44 (0.5%) were HIV-2 sero-positive, two (0.02%) were dually seropositive, and 9,448 (99.3%) were seronegative. Guinea-Bissau nationality and age >25 years were associated with HIV-2 infection, whereas parity ≤2 was associated with HIV-1 infection. Among women who gave birth to live infants, shorter length of union with the partner and having been married more than once were associated with HIV-2 infection, whereas age ≤25 years was associated with HIV-1 infection. Information gained by this study may help target intervention strategies for preventing maternal HIV infection and understanding biological differences between the two viruses.