Asthmatic patients with nasal polyposis (NP) have been reported to have a high prevalence of bronchial hyperresponsiveness (BHR) and a worsening of quality of life (QoL). The aim of this case-control study was to evaluate if NP is a determinant of BHR and is responsible for modifying the QoL in asthmatic subjects. Eighty-nine asthmatic subjects, including 24 patients with NP and 65 patients without NP (controls), underwent spirometry, methacholine challenge test (MCHt), skin prick tests, and were evaluated with the Asthma Quality of Life Questionnaire (AQLQ). Results of the MCHt test are expressed as the provocative concentration of methacholine that causes 20% (PC20) fall of forced expiratory volume at 1 sec (FEV1). The PC20 (mean +/- SD) in NP cases was 1149 +/- 668 microg/ml vs 894 +/- 691 microg/ml in controls (p <0.001). This demonstrates that BHR was not enhanced by the presence of NP in asthmatic subjects. No significant differences were found between the NP cases and controls for overall QoL or for single QoL domains. This study shows that the presence of NP did not impair the QoL of asthmatic patients, as indicated by the items included in the AQLQ questionnaire.