cis-Diamminedichloroplatinum(II) (CDDP) was given as a single agent at a dose of 25 mg/m2 daily for 5 days by continuous infusion; treatment was repeated every 4 weeks in 30 previously untreated patients with advanced non-small-cell lung cancer (NSCLC). The median age of the patients was 61 years; 13 patients had limited disease and 17, extensive disease. The overall response rate was 40% (12/30; 95% confidence limits, 23-58%), with a median survival of 8 months. Vomiting was observed in 37% of patients; elevated serum creatinine levels (greater than 1.5 mg/dl), in 7%; leukopenia (less than 3,000/mm3), in 39%; thrombocytopenia (less than 70,000/mm3), in 26%; and anemia (hemoglobin less than 9.5 g/dl), in 60% of patients. In all cases, these toxicities were mild and transient, requiring no dose modification. The exposure to filterable platinum, determined from the area under the concentration-time curve, was 9.08 +/- 3.21 micrograms h ml-1. We conclude that CDDP given by 5-day continuous i.v. infusion is safe and effective for treatment of NSCLC.