Nedocromil sodium is a non-steroidal prophylactic agent developed for the management of asthma. We have assessed the steroid sparing potential of inhaled nedocromil sodium 4 mg four times daily in a randomized, double blind, placebo controlled study in 69 asthmatic subjects controlled on inhaled beclomethasone dipropionate in the dose range 1000-2000 micrograms daily. Following a 4 week run-in period subjects added nedocromil sodium or placebo by metered dose inhaler to their usual medication for a further 4 weeks. The dose of inhaled steroid was then reduced at fortnightly intervals according to a predetermined schedule, with monitoring of asthma severity, symptom scores, bronchodilator use and peak flow recordings. Sixty subjects entered the steroid reduction phase and achieved median (range) % decreases in steroid dose of 80 (17-100)% with nedocromil sodium compared to 65 (0-100)% with placebo (P = 0.34) with 14 patients in the nedocromil sodium group and 10 in the placebo group being withdrawn completely from inhaled steroids. Subjective global assessment scores were significantly better with nedocromil sodium (mean 2.14) than with placebo (2.93; P < 0.02) though there was no difference between individual daily symptom scores. In this study therefore in asthmatic patients controlled on high doses of inhaled steroids, nedocromil sodium was well tolerated but the small differences in steroid sparing effect between nedocromil and placebo were not statistically significant.