A 1991 serosurvey in a Ugandan trading town on the trans-African highway reported a 40 per cent HIV-1 prevalence in adults. Three years later in a repeat survey of the 531 adults resident in 1991, 279 (53%) were still present, 196 (37%) had left and 56 (11%) had died. There were 138 new residents and 46 children had become adults, making a total of 463 adults in 1994, 13 per cent less than 1991. Most immigrants (91%) came from the surrounding rural district whereas 38 per cent of emigrants went to an urban area. A significant inverse association between wealth and seropositivity was found for women but not men. Of the original residents 157 were known to be HIV-1 positive in 1991; 31 (20%) had died compared to 10 (4%) of the 232 known to be seronegative, representing an HIV-1 attributable mortality fraction of 60 per cent.