Multiple myeloma (MM) in three human immunodeficiency virus (HIV)-infected patients is reported. HIV infection predisposes to the development of high-grade B-cell lymphomas, but few cases of plasma cell tumours in association with HIV have been reported. The coincidence of HIV infection and neoplasia highlights the distinct roles of immunodeficiency and infection with herpesviridae, including HIV itself, in the pathogenesis of HIV-related tumours. In addition, a number of cytokines (e.g., interleukin-6 [IL-6]) and angiogenic factors (e.g., vascular endothelial growth factor [VEGF] and basic fibroblastic growth factor [bFGF]) may play a role in the initiation, maintenance, and progression of multiple myeloma (MM). Infection was the first clinical consideration to the cause of the illness in two of our HIV-seropositive patients. The diagnosis of MM may be difficult in patients with advanced HIV infection as they often have renal failure, bone marrow plasmacytosis, repeated infections, and polyclonal hypergammaglobulinaemia, due to HIV infection itself, opportunistic pathogens, and/or medication.