Eighteen previously untreated patients with squamous cell carcinoma of the lung were treated with a combination of a new bleomycin derivative, peplomycin and esquinon (PQ). One patient achieved a complete response (5.5%) and 5 patients a partial response (27.8%). Overall response rate was 33.3%. Median survival time of 6 patients with complete and partial response was 54 weeks and that of 12 patients with no change and progressive disease was 15 weeks. Toxicities included nausea and/or vomiting in 89%, fever in 61%, interstitial pneumonitis in 28% and leukopenia in 17%. PQ regimen appears to be effective in the treatment of squamous cell carcinoma of the lung.