gamma delta T-lymphocytes have been suggested to play a role in granuloma formation and to participate in the immune responses observed in tuberculosis and sarcoidosis. To further evaluate the role of gamma delta T-lymphocytes in these disorders, we used immunohistochemical techniques and specific monoclonal antibodies to characterize the number of distribution of T-lymphocytes expressing alpha beta and gamma delta T-cell receptors in granulomatous lesions from patients with sarcoidosis (n = 8) or tuberculosis (n = 4). The vast majority of T-lymphocytes present in lymph nodes from patients with tuberculosis or sarcoidosis expressed alpha beta TCR, whereas only rare gamma delta T-lymphocytes were observed inside or at the periphery of the granulomas. Recently formed granulomas induced by positive Kveim test reactions in patients with sarcoidosis also contained only small numbers of gamma delta T-lymphocytes, including those present in biopsies from two patients with increased numbers of circulating gamma delta T-lymphocytes. These observations demonstrate that T-cells involved in immune granulomatous reactions in sarcoidosis and tuberculosis express predominantly alpha beta TCR, and they do not support the conclusion that gamma delta T-lymphocytes necessarily play an important role in granuloma formation.