PURPOSE: To investigate prognoses of lung cancer patients prospectively enrolled in the Japan Lung Cancer Registry Study. METHODS: Patients newly diagnosed as having lung cancer exclusively in 2002 were enrolled. Follow-up surveys were performed twice, in 2004 and 2009, and the final follow-up data with prognoses were analyzed for 14,695 patients (79%). Clinical stages were defined according to the sixth edition of the International Union Against Cancer--tumor, node, metastasis classification (2002). RESULTS: The mean age was 67.1 years (range, 18-89 years), and there were 10,194 men (69.3%) and 4315 women (29.7%). The most frequent histology was adenocarcinoma (n = 8325, 56.7%), followed by squamous cell carcinoma (n = 3778, 26%) and small cell carcinoma (n = 1345, 9.2%). The distribution of clinical stages was as follows: IA, 4245 cases (29.3%); IB, 2248 (14.5%); IIA, 208 (1.4%); IIB, 918 (6.3%); IIIA, 1700 (11.8%); IIIB, 2110 (16.3%); and IV, 3037 (21.0%). The 5-year survival rates were 44.3% for all patients, 46.8% for those with non-small cell lung cancer, and 14.7% for those with small cell lung cancer. According to the clinical stage of non-small cell lung cancer and small cell lung cancer, the 5-year survival rates were 79.4 and 52.7% for stage IA, 56.9 and 39.3% for IB, 49.0 and 31.7% for IIA, 42.3 and 29.9% for IIB, 30.9 and 17.2% for IIIA, 16.7 and 12.4% for IIIB, and 5.8 and 3.8% for IV, respectively. CONCLUSION: Analysis of a large cohort in the Japanese registry study found that stage-specific prognosis was within a range similar to other reports. The data presented should provide an important reference for future clinical trials in Japan.