Herpesvirus-like DNA sequences have been identified in a high proportion of both AIDS-associated and classical Kaposi's sarcoma, and in a small percentage of AIDS-associated malignant lymphomas. To determine the extent of involvement of this new agent designated HHV-8 (human herpesvirus type 8) or KSHV (Kaposi's sarcoma-associated herpesvirus) in human malignant lymphomas, we analyzed 24 AIDS-associated lymphoid malignancies and 100 non-AIDS-associated lymphomas by PCR and Southern blot analysis. Three of 24 lymphoid malignancies from patients with AIDS demonstrated HHV-8 sequences by Southern blot and PCR analyses. The fourth was positive by PCR only. None of the non-AIDS-associated lymphomas contained HHV-8 sequences. All three Southern blot positive samples were derived from extranodal regions, two from pleural effusions, and one from a soft tissue mass in the thigh. This latter patient initially presented with a pleural effusion. The fourth PCR positive but Southern blot negative tumor was from a gingival lymphoma in a patient with a history of Kaposi's sarcoma. All tumors positive for HHV-8 were also positive for EBV. These results confirm a recent report that this novel herpesvirus may play a role in AIDS-associated lymphomas especially in those with body cavity presentation.