During October, 1987, 593 sera were collected from risk groups in Sudan's only major deepwater port, Port Sudan. The risk groups included prostitutes, lorry drivers and prisoners. A large proportion of the study participants practised high risk behaviour which included sexual promiscuity, medical treatment by injection, scarification and tattooing. Despite high risk behaviour and evidence of a high prevalence of hepatitis B infection, a virus transmitted in a manner similar to HIV, no study participants were positive for HIV infection. This data suggests that the prevalence of HIV infection amongst high risk groups in Port Sudan is very low. These findings confirm a lack of clinical cases of AIDS in hospitalized patients in Port Sudan and the small number of reported cases in other areas of northern Sudan.