We report a case of perianal non-Hodgkin's lymphoma that presented as a perianal abscess in an otherwise asymptomatic intravenous drug abuser who tested positively for human immunodeficiency virus infection. Extranodal lymphoma of the anal canal is a very rare event, which has recently been described in homosexual men with the acquired immunodeficiency syndrome. This is the first report, to our knowledge, of perianal lymphoma occurring in a nonhomosexual patient with the acquired immunodeficiency syndrome.