BACKGROUND We have aimed to determine the sensitivity and specificity of a simpler technique with less risk than oral provocation to diagnose aspirin-induced asthma (AIA). METHODS We studied a group of 20 AIA patients compared to a control group with 40 aspirin-tolerant patients (confirmed by oral provocation test): 10 asthmatic patients and 30 healthy subjects. A nasal provocation test (NPT) with lysine acetylsalicylic acid (L-ASA) was carried out. Nasal and pulmonary functions were monitored with anterior active rhinomanometry (AAR) and spirometry. An L-ASA solution (900 mg/ml L-ASA, equivalent to 500 mg/ml acetylsalicylic acid) was diluted with saline solution. We administered four increasing doses: 5, 25, 50 and 100 mg/ml acetylsalicylic acid (ASA) with saline solution control. Nasal and pulmonary functions were monitored with rhinomanometry and spirometry. The patients were controlled for nasal inspiratory peak flow and expiratory peak flow. RESULTS The results showed high sensitivity and specificity: 80% and 92.5%, respectively, with an 84.2% positive predictive value and an 89.2% negative predictive value. The patients had no bronchial or systemic symptoms, and no decreases over 20% were recorded in the FEV1. CONCLUSIONS NPT has a high sensitivity and specificity in the diagnosis of AIA. An oral provocation should be performed to confirm the result whenever the clinical situation of the patient permits it.