It is known that in some asthmatic subjects the administration of acetylsalicylic acid (ASA) and non-steroid anti-inflammatory drugs (NSAID) results in bronchodilatation. We have administered 750 mg of ASA intravenously to 100 asthmatic patients who were without history of ASA intolerance. Functional assessment (FEV) was performed under basal conditions and after 5, 10, 15, 30, 60, 90, 120, 150 and 180 minutes after the administration of ASA. 64 patients had no functional variations, 14 showed a percentage variation of less than 20% in FEV and 14 had a doubtful bronchodilatation (FEV 15-20%). The test was repeated after an interval of 1 week in those patients who showed an increase of 20% in FEV and only 2 confirmed the bronchodilatation. The pathogenesis of asthma that is improved by ASA is not entirely clear, but it is an extremely interesting model for study of the role of different mediators in the asthma syndrome.