Fifty-four patients whose disease had been staged as extensive small cell carcinoma of the bronchus were randomised to receive either CAV1 (cyclophosphamide 600 mg m-2 i.v., adriamycin 50 mg m-2 i.v., given on day 1, and etoposide 500 mg m-2 p.o. given on day 3) or CAV5 (cyclophosphamide and adriamycin given as for CAV1, etoposide 500 mg m-2 given in divided dose over days 3-7) on a 21-day schedule. The two regimens proved comparable (CR + PR 55% vs 56%), and the survival curves were virtually superimposable (median survival: CAV1, 8 months; CAV5, 9 months). Only five patients are still alive. The toxicity of the two treatments was similar. The scheduling of etoposide over 1 or 5 days seemed clinically unimportant in this study, perhaps because of concurrent use of other effective chemotherapy drugs.