Generalized, persistent lymphadenopathies were observed in homosexual men and considered a possible prodrome of acquired immune deficiency syndrome (AIDS). To evaluate these lymphadenopathies, 25 lymph node biopsy specimens from homosexual men with lymphadenopathy (18), lymphadenopathy associated with AIDS (five), and lymphadenopathy associated with non-Hodgkin's lymphoma (two) were reviewed and correlated with the clinical symptoms. In the absence of opportunistic infections, the lymph node lesions were essentially uniform and represented acute inflammatory processes resembling those commonly seen in viral lymphadenitides. This suggests that a lymphotropic agent, probably a virus, causes AIDS as a result of its destructive effects on certain populations of lymphoid cells.