This prospective study evaluates the histopathological findings on 613 patients undergoing curative resection of a bronchus carcinoma and operated on between January 1982 and September 1984. The WHO rules for tumor classification and grading, and the 1979 pTN classification rules of the UICC were followed. Taking into account the biological properties of the tumors and the patient survival times, the prognostic value of histopathological data is discussed. Apart from the clear general dependence of the average survival time on the tumor cell type, it was found that tumor volume is of greater prognostic value with respect to patient survival than tumor diameter.