Although the mechanism of aspirin-induced asthma and rhinitis is unknown, it has been suggested that adverse nasal and bronchial reactions are caused by an increased production of lipoxygenase products. In examining this hypothesis we have measured the release of peptide leukotrienes (PeptLTs), 15-HETE, and prostaglandins in nasal fluids obtained by nasal lavages after instillation of acetylsalycilic acid (ASA) and placebo (saline). Ten ASA-sensitive asthmatics, 10 ASA-insensitive asthmatics, and seven healthy subjects were challenged in a double-blind study with normal saline and 12 mg of ASA. Twelve mg were administered based on the results of a previous study that showed that this dose caused minor to moderate symptoms in ASA-sensitive patients. PeptLTs, LTB4, 15-HETE, PGE2, PGF2 alpha, and PGD2 were measured by radioimmunoassay methods. Significant levels of PeptLTs were detected in sensitive asthmatic patients 60 min after nasal challenge. This change was associated with a significant increase in symptoms. No increase in PeptLTs levels were found, however, in either insensitive patients or healthy subjects. Inhibition of PGE2 and PGF2 alpha release was detected in the three groups after ASA administration. ASA also inhibited PGD2 release in insensitive asthmatic patients but not in both sensitive patients and healthy subjects. These results suggest that an abnormal release of PeptLTs in ASA-sensitive asthmatic patients contributes to nasal and bronchial adverse reactions. The lack of effects on PGD2 release suggests that mast cells from ASA-insensitive patients are more sensitive to ASA than those from sensitive asthmatic patients and healthy subjects.