Simultaneous measurements of serum tissue polypeptide antigen (TPA) and carcinoembryonic antigen (CEA) were conducted on 106 patients with bronchogenic carcinoma and 19 patients with inflammatory pulmonary disease. The distribution of cell types was 63 with adenocarcinoma, 26 with epidermoid carcinoma, 9 with small cell carcinoma, 4 with large cell carcinoma and 4 with adenosquamous carcinoma. There were 20 patients in stage 1, 6 in stage 2, 38 in stage 3 and 42 in stage 4 of their disease. The cut-off values of TPA and CEA were 110 U/L and 3 ng/ml, respectively. The diagnostic sensitivity of TPA and CEA was 61% (65/106) and 47% (50/106), respectively. The diagnostic specificity of TPA and CEA was 90% (17/19) and 95% (18/19), respectively. In combination with TPA and CEA the diagnostic sensitivity and specificity to indicate at least one positive result was 73% and 84%, respectively. Both TPA and CEA revealed significantly higher mean serum levels in stage 4 patients than in stage 1 patients. The intermarker correlation between the serum levels of TPA and CEA was low in this study. Serial measurements of serum TPA after surgical resection were found to be useful in the monitoring of recurrence of tumors.