Forty-five patients with moderately severe perennial bronchial asthma were challenged by ingestion of: acetylsalicyclic acid (ASA); 4 azo dyes (tartrazine, sunset yellow, amaranth, and ponceau); 3 non-azo dyes (erythrosine, brilliant blue, and indigotin); sodium benzoate (NaB); parahydroxybenzoic acid (OHBA); butylated hydroxyanisole (BHA); and butylated hydroxytoluene (BHT). A fall in forced expiratory volume is one second (FEV1) greater than 25% from baseline was considered positive. Seven patients who gave an unequivocal history of aspirin intolerance were not challenged with ASA; an additional 13 had positive open challenges to ASA, giving an apparent incidence of aspirin sensitivity of 20/45. The presence of nasal polyps, simusitis, or the regular use of corticosteroids, either singly or in combination, was not associated with an increased incidence of reactions to ASA. Significant bronchoconstriction to open challenges with agents other than ASA was less frequent. Positive open challenges to all substances except aspirin were followed by double-blind challenges which were positive in only 3 instances: 1 each with erythrosine, ponceau, and NaB/OHBA. Our findings confirm that ASA intolerance is relatively common but suggest on the other hand that reactions to dyes and preservatives are uncommon cause of clinically significant bronchoconstriction in moderately severe perennial asthmatics.