Sixteen cases of histologic intermediate-grade and high-grade AIDS-associated non-Hodgkin's lymphoma (NHL) were studied for the presence and patterns of c-myc gene and bcl-2 locus rearrangements. The presence of Epstein-Barr virus (EBV) sequences and proteins and HTLV-I sequences were also investigated. c-myc gene rearrangements analogous to those observed in sporadic Burkitt lymphomas were detected in 12 of 16 cases. Six of 16 cases had detectable EBV sequences and proteins. None of the cases displayed bcl-2 rearrangements or contained HTLV-I sequences. These data suggest a frequent role for c-myc activation in the pathogenesis of AIDS-associated NHL, independent of histologic type. Conversely, EBV does not appear to be directly involved in lymphomagenesis in the majority of AIDS-associated NHLs.