The aim of our study was to verify the functional modifications affecting central and peripheral airways during bronchoconstriction induced by aerosolized aspirin, so as to better understand the pathophysiologic mechanisms of the asthmatic crises in A.S.A. sensitive patients. The preliminary results were presented of a study carried out o 12 asthmatic A.S.A. sensitive patients, 7 of whom were females and 5 males, between the ages of 22 and 57 years. A.S.A. sensitivity was found in their medical history, in some cases, it had been confirmed by oral A.S.A. challenge. Among these patients, 6 were also affected by nasal polyposis. The method used was recently described by Bianco et al. although slightly modified by us: a fresh aqueous solution (18%) of A.S.A. -L is diluted 1:3 in saline; 4 ml of this solution is transferred to a glass nebulizer activated by a small compressor. The patients underwent treatment for 60 sec, during which a dose of approximately 1,8 mg of A.S.A. was inhaled, corresponding to about 40 mg of aspirin taken orally. In comparison with the reactions induced by oral challenge, those obtained with this treatment are easier, faster and confined only to the respiratory system. Before giving A.S.A. to the patients, control tests using saline aerosol were done. The functional assessment was performed under basal conditions, and 1, 15, 30, 60, 90 and 120 minutes following administration of A.S.A. since bronchoconstriction caused by nebulized A.S.A. usually reaches peak values between the 60th and 90th min. after which it gradually decreases over the following two hours. Our results show that, though A.S.A. induced bronchoconstriction prevails at large airways, it also influences the distal tracts of the tracheobronchial tree, since both SRAW, FEV1 and Vmax50C are modified at the same time.