In an attempt to determine the prognostic significance of pretreatment factors for patients with advanced non-small cell lung cancer (NSCLC), 24 pretreatment clinical variables were analyzed for 185 patients with NSCLC who underwent chemotherapy and/or radiotherapy between 1985 and 1994. Following univariate analysis, we applied two multivariate statistical techniques. In a Cox regression mode, independently significant factors influencing patient survival included performance status (PS), disease stage, hemoglobin level, and serum calcium level. Recursive partitioning and amalgamation (RPA) resulted in three distinct prognostic subgroups based on PS, stage, weight loss, and hemoglobin level. The best survival was observed for patients with a good PS and Stage III disease who had a hemoglobin level > 11 g/dl. The worst survival was observed for patients with a poor PS and presence of weight loss irrespective of stage. All other patients had an intermediate prognosis. Median survival times were 95.1 weeks, 17.1 weeks and 39.3 weeks, respectively (P < 0.00005). The results of our analyses show that three important prognostic subgroups could readily be discerned using RPA.