Thirty-eight patients with non-resectable non-small-cell Stage IIIa-b lung cancer were treated in a Phase II study with radiotherapy (50 Gy in a 25-fraction split-course) plus con-current continuous infusion of cisplatin given at a daily dose of 6 mg/m2, with the aim of investigating its radiopotentiation properties. Treatments were given on an outpatient basis by means of a central venous catheter and a portable pump. Adjuvant surgery was undertaken when feasible. Toxicity was mild to moderate. The probability of a partial or complete locoregional response at 4 weeks after treatment completion was 83% (confidence limits at 95%: 13). Eighteen patients were resected. Overall 1-, 2- and 3-year progression-free survival probabilities were 42, 24 and 21%. These figures were 63, 37 and 24% in observed survival curves. Patients with squamous-cell tumors had observed survival rates of 82, 50 and 28% at 1, 2 and 3 years, compared to 42, 19 and 19% in patients with non-squamous histology. The high response and survival rates obtained at a low price according to toxicity require further investigation.