The increase in neutrophil chemotactic activity (NCA) is related to mast cell degranulation. This study was performed in 10 patients in whom aspirin-induced urticaria was connected with increased NCA. A state of tolerance to aspirin (ASA) was achieved by administering incremental doses of acetylsalicylic acid. In none of the examined Patients was an increase in NCA observed after 600 mg of ASA given after desensitization. The authors conclude that in patients with ASA-induCed urticaria, mast cell degranulation does not occur after ASA desensitization.