This study sought to address the relationship of primary pulmonary carcinoma (PPC) with P16 protein expression. The expression of P16 protein in 65 cases of PPC was examined with immunohistochemical staining. The rate of loss of P16 protein expression in PPC was 36.92% +/- 18.45%. The rate of loss of P16 protein expression in adenocarcinoma (AC) was 28.47 +/- 16.33%, that in squamous cell carcinoma (SCC) was 35.95% +/- 17.36%, and that in adenosquamous cell carcinoma (ASCC) 57.88% +/- 10.18%. There significant differences were in the rate of loss of P16 protein expression between those aged < 60 with SCC and those aged > 60 with SCC, between low differentiated PPC and intermediate differentiated PPC, between AC and ASCC, and between SCC and ASCC (P < 0.05). There were no significant differences in the rate of loss of P16 protein between males and females with PCC, between left and right PPC, and between PPC and metastatic pulmonary carcinoma of lymph node (P > 0.05). These suggest that P16 protein expression may be one of the important standards in estimating the prognosis of patients with PCC.