Immunologic prognostic factors in lung cancer have not been fully clarified. We report the results of a prospective study undertaken to clarify the correlation between various cellular immunologic parameters and the survival of lung cancer patients. A total of 287 lung cancer patients were enrolled in this study. Representative in vitro cellular immune activities including lymphoblastogenesis and natural killer cell activities, in addition to the percentage of main lymphocyte subsets (CD3, CD4, CD8, HLA-DR, and Fc gamma R III on T cells) in the peripheral blood were evaluated before the initiation of therapy. The immune factors that influence the prognosis were analyzed by the log rank test and a multivariate analysis using the Cox proportional hazards model. Univariate analysis of the survival curves revealed a significant difference with regard to disease stage (P<0.0001), age (P=0.007), gender (P=0.0037), and HLA-DR (%) (P=0.048), when all the non-small cell lung cancer (NSCLC) patients (n=257) were analyzed together. This analysis, based on the histologic type, revealed that HLA-DR (%) was a significant predictor of survival in squamous cell carcinoma (P=0.0013) and small cell carcinoma (P=0.0025). A decreased CD4/CD8 ratio in small cell carcinoma (P=0.0062) and male gender in adenocarcinoma (P=0.0086) were factors associated with a worse prognosis. Multivariate analysis identified a significant correlation between survival and disease stage (P<0.0001) and gender (P=0.0243) in adenocarcinoma, disease stage (P<0.0001), age (P=0.0436) and HLA-DR (%) (P=0.0142) in squamous cell carcinoma, and HLA-DR (%) (P=0.0212) and CD4/CD8 (P=0.0112) in small cell carcinoma, suggesting independent prognostic significance. A variety of immunologic indices have prognostic significance for the different types of lung cancer. Among these, the HLA-DR (%) in the peripheral blood is the most reliable factor for squamous cell carcinoma and small cell carcinoma.