A review of 40 cases of peripheral T-cell lymphoma identified at our institution between March 1983 and December 1985 revealed a clinically, histologically, and immunologically diverse group of neoplasms that were difficult to classify by conventional histomorphologic criteria for non-Hodgkin's lymphomas. These lymphomas were frequently extranodal at the time of initial manifestation (52%), and their clinical aggressiveness correlated with three major histologic categories--small lymphocytic, diffuse mixed, and large cell. Of the 40 lymphomas, 18 exhibited distinctive histologic features that allowed assignment of these cases into one of four subgroups: (1) angioimmunoblastic lymphadenopathy, (2) lymphomatoid granulomatosis, (3) Hodgkin's-like disease, and (4) Lennert's lymphoma (lymphoepithelioid lymphoma). Study of all our cases that fulfilled the morphologic criteria for lymphomatoid granulomatosis or angioimmunoblastic lymphadenopathy by using immunologic methods for identification of B-cell and T-cell antigens has shown these neoplasms to be peripheral T-cell lymphomas. Therefore, we now consider these earlier proposed entities to be distinct histologic variants of peripheral T-cell lymphoma.