The effects of chemotherapy by single administration of Cisplatin were studied in 26 patients with non-small cell carcinoma of the lung. There were 22 males and 4 females with a median age of 63 years. 21 cases were epidermoid carcinoma, 4 cases were adenocarcinoma and 1 case was atypical carcinoid. Cisplatin 20 mg/m2 with hydration and diuresis was given daily for 5 consecutive days. The course was repeated every 3 weeks. Partial response was observed in 4 patients (3 epidermoid carcinoma and one atypical carcinoid). The response rate was 19%. Side effects induced by Cisplatin were gastrointestinal toxicity including vomiting, nausea and appetite less, bone marrow toxicity and renal damage. These were not so severe, and reversible. Gastrointestinal toxicities were controlled successfully by corticosteroids. In 12 patients gastrointestinal toxicities were not observed. We conclude that Cisplatin is effective for non-small cell carcinoma, especially for epidermoid carcinoma. Hematologic toxicities of Cisplatin were not so severe. Therefore, combination chemotherapy including Cisplatin would improve the quality of life of patients suffering from non-small cell carcinoma of the lung.