Aim: Asthma affecting elite athletes has been studied mainly in subjects practicing winter sports. The aim of our study was to test the pulmonary function in order to evaluate bronchial hyper-responsiveness prevalence in a team of 25 male professional cyclists (27.9+/-3.9 years old with a VO(2max) equal to 69.9+/-6.6 mL.min(-1) x kg(-1))., Methods: Using a questionnaire that queried the presence or absence of asthma history or common symptoms of exercise induced bronchospasm, 72% of the subjects had upper airway or bronchial symptoms. Using a pneumotachograph, we recorded a forced flow-volume curve at rest, after a maximal exercise test with ambient air, and after beta2-agonist inhalation, then during a methacholine challenge., Results: In our study, 52% of the subjects showed clinical symptoms associated with bronchial responsiveness during methacholine test, a proportion which is much higher than the average population (3-20%). However, ERS-ATS pulmonary function testing criteria at rest (reduced FEV1, FEV1/FVC, FEF25-75%) were not fulfilled by any of them. In the asthmatic group, O2max was significantly higher (70.5+/-6 vs 68.6+/-8.2 mL.min-1.kg-1, P<0.05). This remained true for submaximal loads suggesting that ventilation energy cost related to bronchial hyper-responsiveness was also higher., Conclusions: We have reported in this study that professional cyclists have a far higher prevalence of bronchial hyper-responsiveness than the average population, which can be regarded as a real health issue.