The survival rates of 90 patients who underwent operation for bronchogenic carcinoma were analyzed statistically according to sex, age, tumor stage and histologic type, types of surgical procedures (lobectomy or pneumonectomy), and to immunomorphologic parameters of immunologic activity in peribronchial and hilar lymph nodes. The Stage I group survived significantly longer than did the Stage II and III groups, the lobectomized patients survived significantly longer than the pneumonectomized patients. The absence or presence of lymph node metastases was one of the major determinants of survival. The mean values (percent of total node cut surface) of lymph node sinus histiocytosis and of paracortical area could be correlated directly to survival in each of the histologic tumor-type groups, while the development of follicular cortex and germinal centers correlated inversely with survival. Increased survival might be associated with changes concomitant with immune reactivity in lymph node T-cell areas and with the sinus histiocytosis pattern, the latter representing probably a tumor--host reaction of the delayed hypersensitivity type. By contrast, increased activity of lymph node B-cell areas tended to correlate with poor prognosis of lung cancer patients. Moreover, patterns showing germinal center hyperplasia were statistically associated with lymph node neoplastic invasion, while the pattern with sinus histiocytosis and expanded paracortical areas was statistically associated with tumor-free lymph nodes.