INTRODUCTION: Hypersensitivity reactions to drugs account for 25% of all side effects related to drugs, affecting more than 7% of the population. One in four such reactions is caused by acetylic acid and other non-steroidal anti-inflammatory drugs. MATERIAL AND METHODS: Between 1998 and 2000 epidemiological research was carried out in various centers, with the aim of estimating the frequency of allergy-based diseases in Poland. The objective of the study was to evaluate the frequency of hypersensitivity to non-steroidal anti-inflammatory drugs (NSAIDs), based on an epidemiological questionnaire, in the Polish adult population. RESULTS: Bronchial asthma was diagnosed in 582 patients (5.4%). Of that group, 75 patients (12.9%) additionally reported symptoms of hypersensitivity to NSAIDs. Aspirin-induced asthma was diagnosed in 11 patients (14.7%) with clinical manifestations of hypersensitivity responses. Frequency of aspirin-induced asthma with clinical symptoms amounted to 1.9% of asthmatics. In the assessment of severity of the disease, aspirin intolerance was the only statistically significant factor (p = 0.0003; odds ratio 28.6 with assumed 95% confidence interval). CONCLUSIONS: In the population of adults in Poland, the frequency of aspirin-induced asthma amounted to 0.1%. Hypersensitivity to NSAIDs was observed in 12.9% of asthmatics. In asthmatics with symptoms of hypersensitivity to non-steroidal anti-inflammatory drugs, which takes the course of clinically demonstrable aspirin-induced asthma, the risk of severe asthma is 30-fold higher.