At present provocation tests are indispensible tools for diagnosing acetylsalicylic acid (ASA) intolerance, which is often associated with nasal polyps. Reliable oral and inhalation provocation tests are time-consuming procedures that often cause the patient discomfort because of accompanying reactions. These tests are therefore best done with the patient hospitalized. Studies concerning the sensitivity, specificity and tolerance of the new intranasal provocation procedure using lysine-ASA were based primarily on cases of bronchial asthma and yielded differing results. Our aim was to examine the above parameters in a large group of patients with nasal polyps (n = 153) and to compare this method with the oral ASA procedure. Intranasal provocation with 2 mg lysine-ASA revealed a sensitivity of 0.47 (n = 30) and a specificity of 0.91 (n = 105), with the test period lasting 40 min. A modified provocation test with 2, 4 and 10 mg lysine-ASA and a 100 min test period resulted in a sensitivity of 0.67 (n = 15) and a specificity of 0.84 (n = 37). All in all, only 2 patients reacted to the test with signs of bronchial asthma. Other reactions to the provocations were limited to the upper respiratory tract or were only found with rhinomanometry. These findings show that nasal provocation with lysine-ASA can be helpful in determining whether an oral provocation test is indicated. The procedure does not take very long, is well-tolerated and can be done in the outpatient department.