Forty-four HIV-1-seropositive women and their children were followed-up and examined in connection with the course of pregnancy, mother-to-infant transmission of HIV and clinical outcome. Twelve out of 48 children were known to be infected and two children were lost to follow-up. Of the remaining 34 children, 22 are not infected, and 12 are clinically and immunologically normal at less than 18 months. There was no difference in intrauterine growth between infected and uninfected children. Forty-six per cent of the 39 mothers seen after delivery progressed to a more advanced stage of HIV infection during a mean follow-up time of 33 months after delivery. Although comparable in age, clinical and immunological status at delivery, and follow-up time, mothers of infected children had longer durations of HIV infection and were symptomatic and/or had low CD4 cell counts to a significantly greater extent at follow-up than mothers of uninfected children.