In a 12-week study 20 children, ages two to seven years, with moderate to severe asthma received 20 mg cromolyn sodium via a power-driven nebulizer four times daily. Entry criteria required that each patient be maintained on at least one bronchodilator on a daily basis prior to the study. By the conclusion of the trial asthmatic symptoms had declined significantly (p less than 0.01), both as scored by the patients and by the physician. These was a 73% reduction in theophylline dosage over-all. No significant adverse reactions occurred, and there were no meaningful changes in clinical chemistry tests hematology or urinalyses.