A 76-year-old male patient was diagnosed with advanced double cancer of the lung and stomach. He had also been suffering from interstitial pneumonitis for several years. He was treated with combination of cisplatin and TS-1. TS-1 (120 mg/body/day) was administered for 21 days from day 1, and cisplatin (60 mg/m(2)) was given on day 8 followed by a 14-days interval. After two courses of chemotherapy,the dose of cisplatin was reduced to 48 mg/m(2) because of grade 1 serum creatinine elevation. The lesions of the lung and stomach were improved significantly without exacerbation of the interstitial pneumonitis.