The use of nedocromil sodium 4 mg q.i.d. in asthmatics with mildly unstable asthma induced by a reduction of their inhaled beclomethasone dipropionate dose was investigated in a double-blind, parallel group, placebo-controlled study. Compared with placebo, nedocromil sodium improved night-time and daytime asthma score, night-time and daytime bronchodilator use, and evening PEFR at some stage during the 4-week treatment. It is concluded that nedocromil sodium exerts a beneficial effect in chronic asthma.