18 patients with metastatic or recurrent bronchogenic carcinoma and one patient with a squamous cell carcinoma of the trachea were treated with a combination of CCNU, hexamethylmelamine and methotrexate. Objective remissions were observed in 3/19 (16%): 1 complete, 1 partial (greater than 50%) and 1 incomplete (less than 50%). However, the patient with the complete response was the only drug death, on day 21. Remission duration in the other two patients was 3 and 9+ months respectively. One patient with oat cell carcinoma experienced no tumor progression for 5 months. This combination resulted in severe gastrointestinal toxicity in 5/19, severe thrombopenia in 12/19 and severe neutropenia in 6/19. We conclude that the combination as used here resulted in no increased clinical effectiveness and proved to be quite toxic.