The effect of nifedipine on allergen-induced asthma in nine asthmatic subjects was studied. All subjects had a history of asthma and positive Prick test; lyophilized allergen extracts of Dermatophagoides Pteronyssinus were used. All solutions were inhaled through DeVilbiss nebulizer. On the first day baseline FEV1 value was measured, allergen extracts were inhaled at increasing doses. The procedure was repeated until a 20% fall from the baseline FEV1 was obtained. Nifedipine or placebo capsules were administered sublingually in a randomized double blind manner. Antigen challenge was given 30 minutes later by using provocating dose of allergen. The change in FEV1 value was calculated from the post nifedipine administration. A significant negative correlation (p less than 0.01) was found between the percentage of protection and the baseline PD20. Nifedipine produced a significant mean change of the bronchial reactivity threshold (p less than 0.01).