In an attempt to elucidate the mechanisms involved in analgesic-induced asthma, I performed bronchial and intravenous challenge tests with indomethacin in 5 aspirin-sensitive asthmatics. Bronchial challenge with less than 2 mg of indomethacin elicited bronchoconstriction that developed immediately in most cases, reached its macimum at a mean time of 64 min, and was over within 2 to 4 h. The time sequence of the reaction after intravenous challenge was similar to that after bronchial challenge, except that to obtain a comparable degree of bronchoconstriction it was necessary to administer at least twice the inhaled dose. Inhalation of disodium cromoglycate during bronchoconstriction inhibited the reaction within 8.6 +/- 5.7 min, regardless of the route of challenge. This suggests that sequential mast cell degranulation with liberation of chemical mediators is the mechanism responsible for bronchoconstriction in analgesic-induced asthma.