Cases of non-Hodgkin's lymphoma (NHL) occurring in immunosuppressed patients, including those who are infected with the human immunodeficiency virus, may develop in areas other than the lymph nodes. In AIDS-associated NHL, about 5% of cases of extranodal NHL are intra-oral. This case report describes the presentation of malignant non-Hodgkin's lymphoma in the mouth of a man who had AIDS. The lesion arose on separate occasions at three distinct sites, spontaneously regressing at each site prior to appearing at another intra-oral site.