Serological studies on 7796 rural Ugandans showed 377 (4.8%) were HIV-1 antibody-positive, of whom 343 (8.2%) were adults, ten (0.4%) 5-12-year-olds and 24 (1.7%) under 5 years of age. Serological tests done on 18 mothers of the under-5s showed 17 to be HIV-1-positive. One mother was persistently negative. Her child had a history of multiple injections. Structured interviews with parents or guardians of the ten HIV-1-seropositive children aged 5-12 years to determine possible sources of exposure revealed that six were vertically infected and that blood transfusion, injections and sexual exposure each accounted for one case. It was not possible to identify a source of exposure in one instance. There was no evidence that casual household contact or scarifications played a role in the transmission of HIV-1 in children in this population. Our data show that in this rural population HIV-1 seropositivity in children is mainly associated with seropositivity in the mothers and that HIV-1 infection in children aged between 5 and 12 years is rare.