Pupillary responses to phenylephrine and carbachol and airway reactivity were determined in 19 drug-free persons with mild allergic asthma, 21 nonatopic control subjects, and six asymptomatic atopic control subjects. The concentration of phenylephrine required to dilate the pupil 1 mm, obtained by interpolation on the dose-response curve, was taken as a measure of alpha-adrenergic sensitivity. This concentration was significantly lower for subjects with asthma than for atopic or nonatopic control subjects (1.11 +/- 0.68% [mean +/- SD], 1.86 +/- 0.81%, and 1.52 +/- 0.67%, respectively; p less than 0.05 by analysis of variance). The concentration of carbachol required for pupillary constriction of 1 mm, obtained by interpolation on the dose-response curve, was taken as a measure of cholinergic sensitivity. This value was significantly lower for subjects with asthma than for atopic or nonatopic control subjects (0.23 +/- 0.12%, 0.41 +/- 0.14%, and 0.35 +/- 0.19%, respectively; p less than 0.05 by analysis of variance). Pupillary alpha-adrenergic and cholinergic sensitivity were significantly correlated (Spearman's rank correlation coefficient, Rs = 0.42, p less than 0.05). Both alpha-adrenergic and cholinergic sensitivity of the pupils correlated with airway reactivity expressed as concentration of methacholine causing a 20% fall in FEV1 (Rs = 0.35, p less than 0.05, and Rs = 0.45, p less than 0.05, respectively). The autonomic aberrations cannot be attributed to drug use or significantly abnormal pulmonary mechanics. Autonomic abnormalities are associated with allergic asthma and may contribute to the airway reactivity characteristic of the disease.