The survival curves of primary lung cancers are significantly different by histologic type. The purpose of this study was to analyze the survival curves and prognostic factors of primary lung cancers according to the histologic type at the Tri-Service General Hospital for the years from 1983 to 1988. All records of new patients admitted to TSGH with primary lung malignancies were retrieved from the tumor registry. The survival curve was estimated by Kaplan-Meier Limit Estimate. The prognostic significance of 6 clinical and pathologic factors (sex, age, stage of disease, primary location, histologic differentiation and treatment) were analyzed by single variable analysis and by Cox multivariate regression. There were 448 male and 199 female patients with a mean age of 61.5 years. Adenocarcinoma was the most common histologic type found in both sexes, 37.9% in the men and 72.8% in the women. Patients in the advanced stage with distant metastasis comprised 52.8%. The most frequent location was the upper lobe (37.8%). Methods of treatment were: a) no therapy (39.7%), b) radiotherapy (34.7%), c) surgery with radiotherapy (8.7%), and d) other treatment (16.9%). The median survival of the 647 patients was 6.8 months after diagnosis. The overall one-year, three-year, and five-year survival rates were 26%, 10% and 5%, respectively. Survival curves according to the histopathologic type demonstrated that patients with small cell carcinoma had the lowest cumulative survival and patients with adenocarcinoma had a lower cumulative survival than those with squamous cell carcinoma.(ABSTRACT TRUNCATED AT 250 WORDS)