B-cell lymphoid tumors that occur in association with AIDS. Patients often present with an advanced stage of disease and highly malignant subtypes including Burkitt lymphoma, immunoblastic large-cell lymphoma, small non-cleaved-cell lymphoma and diffuse large-cell lymphoma. The tumors are often disseminated in unusual extranodal sites and chromosomal abnormalities are frequently present. It is likely that polyclonal B-cell lymphoproliferation in AIDS is a complex result of EBV infection, HIV antigenic stimulation, and T-cell-dependent HIV activation.