In a group of atopic adult asthmatic patients the effects of two new inhaled anti-asthmatic drugs, nedocromil sodium and minocromil were studied in two independent randomized double-blind trials to assess their efficacy in preventing exercise-induced asthma (EIA). Exercise testing consisted of steady state running on an inclined treadmill. Neither drug administered 30 min before exercise significantly altered baseline FEV1. Nedocromil sodium (2 and 4 mg) pre-treatment in nine patients and minocromil (4 mg) in eight patients gave significant protection (P < 0.001) compared to placebo as assessed by the reduction in the maximum percentage fall in FEV1. There was no significant difference in the inhibitory effect of the two doses of nedocromil sodium. These results indicate that both nedocromil sodium and minocromil can attenuate EIA.