In a double-blind controlled crossover trial of inhaled disodium cromoglycate and beclomethasone dipropionate in juvenile asthma, beclomethasone produced higher therapeutic scores but significantly so in only two indices--wheeze-free days and morning peak flow rates. Combined treatment offered no advantage over beclomethasone alone. No side-effects were noted. The findings confirm other studies of cromoglycate and a steroid aerosol (betamethasone 17-valerate) but disagree with the only other comparative trial of cromoglycate and beclomethasone, in which both were found equally effective.