Nasal deposition of allergen or histamine could cause bronchoconstriction in subjects with asthma by a reflex mechanism. To investigate this possibility, six atopic subjects with stable asthma and five normal control subjects were studied by nasal-challenge testing with saline, Bermuda grass-pollen allergen, and histamine on paper disks. Challenges were done on 3 separate days by use of a double-blind, randomized trial design. Fivefold serial dilutions were used to determine threshold doses for provocation of at least a twofold increase in the postsaline nasal airway resistance. No patient developed cough or wheezing or required treatment at the end of the nasal-challenge tests, even when persistent sneezing was provoked or in the subject who had a dual nasal response to nasal challenge. In spite of changes in nasal airway resistance that generally conformed to expectations, there were no significant effects of nasal challenge on lung function, including forced expiratory flow rates, vital capacity, residual volume, and partial expiratory flow-volume curves.