In 4.4% of human immunodeficiency virus-associated non-Hodgkin's lymphoma the presenting lesion is seen in the mouth. Often the lesion may clinically resemble a less sinister process, and a definitive diagnosis of lymphoma may be delayed. We describe three unusual cases of non-Hodgkin's lymphoma, appearing intraorally in association with other oral lesions, in HIV-positive homosexual men. The three patients reported here were all diagnosed as having diffuse, large-cell malignant non-Hodgkin's lymphoma. We performed Epstein-Barr virus DNA in-situ hybridization on our cases and Epstein-Barr virus DNA sequences were not seen. We review the pertinent literature and stress the importance of including non-Hodgkin's lymphoma in the differential diagnosis of oral lesions in patients at risk of HIV infection.