A total of 20 patients with loco-regional non-small-cell lung carcinoma were entered into a study of irradiation (3.0 Gy x 15 doses to a total dose of 45 Gy given in 4 fractions per week on days 1, 2, 4 and 5 of each week) and cisplatin given at a dose of 40 mg/m2 on day 3 of each week for a total of three infusions. One patient who had stage 1 disease showed a complete response to therapy and is alive and clear of disease at 35 months. In 19 patients with stage 3 disease, the complete response rate was 16% and the partial response rate was 42%. The rate of 1-year survival was 42% and the rate of 2-year survival was 11%; the median survival of these patients was 11 months. Relapse occurred, mostly at metastatic sites, in 10 of the 11 patients who responded to therapy. Acute toxicity was modest and tolerable by our patients. No severe late toxicity was encountered, and none of the patients developed grade 3 dyspnoea (an inability to walk 100 yards because of breathlessness) while clear of recurrent disease. Changes in lung function observed at follow-up examinations were similar to those seen after irradiation alone. Weekly administration of cisplatin is therefore feasible in patients receiving a continuous course of irradiation. The high relapse rate observed in responding patients indicates the need for evaluation of the efficacy of combination chemotherapy in the adjuvant or neo-adjuvant setting.