In a group of 229 patients with carcinoma of the lung, who were subjected to resection of the tumor during the period January, 1, 1967 to December 31, 1978 at the Surgical Department of the University Hospital at Erlangen, the prognostic significance of the histological type of cancer, and the pTNM classification and stage grouping in the AJC and the UICC classification systems was investigated. Of all the individual prognostic factors, the size of the tumor and the metastatic involvement of the lymph nodes seem to be of the greatest value. These 2 factors, combined in the stage grouping of the AJC and UICC classification systems, provide unequivocal information on the prognosis. The more differentiated subdivisioning of the UICC stage I into la (without lymphatic involvement), and lb (with lymphatic involvement) adds valuable information for the anatomical extension of the tumor at the time of diagnosis or resection, represents the determinative factor for the future fate of the patient. Of the histological types, the epidermoid carcinoma is associated with the most favorable prognosis, but no statistically significant differences are observed among the non-small-cell carcinomas. The poorest prognosis is associated with small-cell anaplastic carcinoma, the difference vis-a-vis the other main types being statistically significant.