Fifty human immunodeficiency virus (HIV)-infected patients with perianal sepsis were studied. Seven (14 per cent) had serious septic complications, four patients with severe necrotizing gangrene, and three with abscesses in the mediastinum, liver and brain respectively. CD4+ lymphocyte counts were significantly lower in patients with severe septic complications as compared with those with uncomplicated perianal sepsis (P < 0.05). In patients with HIV presenting with rare (metastatic) abscesses, perianal sepsis must always be kept in mind as a possible focus. Although HIV-infected patients have a limited life expectancy perianal fistulas and abscesses should be aggressively treated, because of the high risk of severe complications.