BACKGROUND: Some patients with asthma respond poorly to corticosteroids and have persistent airway inflammation and daily clinical symptoms. The aim of this study was to investigate the effects of nedocromil sodium (NS), a nonsteroidal antinflamatory drug, in the treatment of steroid-resistant asthma. METHODS: Steroid-resistant asthma was diagnosed in any patient who demonstrated 20% improvement in FEV₁ after treatment with inhaled salbutamol with failure of FEV₁ to improve by at least 15% after a 2-week trial of prednisolone, 30 mg daily. In a double-blind placebo-controlled trial, the patients received either 4 mg of inhaled NS (n = 13) or placebo (n = 13), 4 times daily for 3 months. RESULTS: NS but not placebo resulted in a mean increase in FEV₁ of 11.4% after 12 weeks of therapy (p = 0.05) and of 12.4% (p = 0.04) and 15% (0.02) in morning peak expiratory flow after 8 and 12 weeks of treatment, respectively. Changes in FEV₁ at 4 and 8 weeks and in peak expiratory flow at 4 weeks of NS therapy were not significant. NS was also effective in reducing variability of peak expiratory flow (p = 0.02) and use of salbutamol (p = 0.005) and in improving quality of life (p = 0.007) by the trial end. Six of the 12 patients treated with NS who completed the treatment period showed a “good response,” defined by a reduction in salbutamol use of more than 50% and an increase in morning peak expiratory flow of more than 20% from baseline; there were no clinical predictors of this response. Two patients were withdrawn from the study because of severe asthma exacerbation (one from each treatment group). CONCLUSION: Inhaled NS improved pulmonary function and decreased asthma severity in steroid-resistant asthma, but its effectiveness is not homogeneous and cannot be predicted from baseline clinical data. (J ALLERGY CLIN IMMUNOL 1996;97:602-10.)