OBJECTIVE: To compare birth outcomes, hospital admissions and mortality amongst HIV-1 seropositive and HIV-1 seronegative pregnant women in Kampala, Uganda and Harare, Zimbabwe. DESIGN: In Kampala and Harare about 400 HIV-1 seropositive and 400 HIV-1 seronegative pregnant women were recruited at initial visit for antenatal care into a prospective study and followed for two years after delivery. The women were classified as HIV-1 seropositive at recruitment if initial and second ELISA tests were positive and confirmed by Western Blot assay. Data on demographic, reproductive, contraceptive and medical histories were obtained using a comprehensive questionnaire at entry, 32 and 36 weeks gestation, at delivery and at six, 12, and 24 months post delivery. In addition, a physical examination and various blood tests were performed at each antenatal and post natal visit. RESULTS: During the two years after delivery, HIV-1 seropositive women had higher hospital admission and death rates than HIV-1 seronegative women. HIV-1 seropositive mothers had a two-fold increase in risk of being admitted to hospital (Kampala: RR = 2.09; 95% CI = 0.95 to 4.59; Harare: RR = 1.98; 95% CI = 1.13 to 3.45). In the six weeks after delivery eight deaths occurred, six of which were among HIV-1 seropositive women and in the period from six weeks to two years after delivery, 53 deaths occurred, 51 of which were among HIV-1 seropositive women (Kampala: RR = 17.7; 95% CI = 4.3 to 73.2; Harare: RR = 10.0; 95% CI = 2.3 to 43.1). However, there was no difference in hospital admission rates between HIV-1 seropositive and seronegative women during pregnancy itself and there was only one death during that period (in a HIV-1 seronegative woman). There was no difference in the frequency of complications of delivery between HIV-1 seropositive and HIV-1 seronegative women and the outcome of births were also similar. CONCLUSIONS: A significant number of HIV-1 positive pregnant women presented at both Harare and Kampala although there was no difference in the number of hospital admissions or mortality between HIV-1 seropositive and HIV-1 seronegative women during pregnancy. Although there were no differences in complications during pregnancy or outcome at delivery, in the two years after delivery, HIV-1 seropositive women in both centres were at increased risk of being admitted to hospital and of dying.