Human herpesvirus-8 (HHV-8) DNA sequences have been reported to be strictly associated not only with various forms of Kaposi's sarcoma but also with an unusual subgroup of acquired immunodeficiency syndrome (AIDS)-related B-cell lymphomas. A possible relation of this putative virus also with multicentric Castleman's disease (MCD) has been recently suggested. We used polymerase chain reaction to look for the presence of HHV-8 sequences in a well characterized series of benign, atypical, and malignant lymphoid tissues from 45 Hodgkin's disease and 43 non-Hodgkin's lymphoma (NHL) cases, as well as from 5 MCD, 15 angioimmunoblastic lymphadenopathy (AILD), and 23 benign lymphadenopathy cases. Among the 38 AIDS-related lymphoid lesions, only 1 NHL and 1 persistent generalized lymphadenopathy (PGL) case were positive. Furthermore, among the 92 non-AIDS-related lymphoproliferative disorders, HHV-8 sequences were detected in 3 classic AILD cases and in 4 reactive lymphadenopathies. Six of 9 HHV-8 positive lymphoid lesions (1 NHL, 1 PGL, 1 AILD, and 3 reactive lymphadenopathy cases) were also positive for Epstein-Barr viral sequences. The four human immunodeficiency virus (HIV) negative lymphadenopathies positive for HHV-8 sequences showed an almost identical histology, characterized by a predominantly follicular lesion, with giant germinal center hyperplasia, and increased vascularity, resembling HIV-related lymphadenopathy and MCD. Our results, while providing the first evidence of the presence of HHV-8 sequences in AILD cases, suggest a possible association of these herpes viral sequences with a distinct histologic type of non-neoplastic lymphadenopathy, not associated with other common herpes infections.