A preliminary phase II study of cis-Dichlorodiammineplatinum (II) was carried out in 17 patients with non-small cell carcinoma (12 adenocarcinomas, 3 squamous cell carcinomas, 2 large cell carcinoma) of the lung, and in 15 patients with metastatic pulmonary tumor. All patients could be evaluated. A partial response was obtained in 2 of 12 adenocarcinoma patients and in 1 of 3 patients with squamous cell carcinoma, resulting in a partial response rate of 17.6%. A partial response was also obtained in one patient each from those with metastatic pulmonary tumor from the uterus, skin and pharynx and in patients with mediastinal tumor, resulting in a partial response rate of 26.7%. There was mild myelosuppression in our patients; renal toxicity and toxic neuropathy seemed to be the dose-limiting factors in cis-Dichlorodiammineplatinum (II) therapy.