Twenty-five ASA-sensitive patients with rhinosinusitis asthma underwent oral ASA challenges followed by desensitization to the adverse respiratory effects of ASA. We then compared the efficacy of continuous ASA treatment for their respiratory tract disease to that of a placebo treatment during a double-blind crossover study. For this group of 25 patients, there was significant improvement in nasal symptoms and a reduction in use of nasal beclomethasone during the months when they received ASA treatment. Lower respiratory tract symptoms, values of FEV1, and the use of antiasthmatic medications including prednisone were not significantly changed during ASA treatment. Desensitization to ASA followed by ASA treatment appears to significantly alleviate symptoms of rhinosinusitis. However, only half the patients experienced improvement in their asthma symptoms during ASA treatment.