This study deals with the immunohistochemistry of a monoclonal antibody (Mab) raised against the p18 protein of the LAV virus in lymphnodes from 20 cases of persistent generalized lymphoadenopathy (PGL) (2) and 6 of acquired immunodeficiency syndrome (AIDS) (3). In all the PGL cases that have been studied, we observed a very important disruption of the follicular dendritic cell's (FDC) framework in the germinal centers which is associated with the presence of an increased number of Leu2a+ lymphocytes inside the germinal centers. This observation is consistent with the main morphological feature of the lymphnodes in the PGL syndrome which is mainly characterized by lesions of FD cells.