Irritable bowel syndrome (IBS) is one of the most common diseases of the gastrointestinal tract. IBS may represent a primary disorder of gastrointestinal motility accompanied with motor dysfunction in various extraintestinal sites. Recent studies suggest that IBS is associated with bronchial hyper-responsiveness and bronchial asthma might be more prevalent in IBS patients than in control subjects. The aim of our study was to assess the prevalence of IBS in a cohort of asthmatic patients. We evaluated 150 patients with bronchial asthma (71 males and 79 females, aged 45.1+/-14.9 years) and two control groups including 130 patients with other pulmonary disorder and 120 healthy subjects. All subjects enrolled (asthmatic and controls) completed the Greek version of the Bowel Disease Questionnaire (BDQ). BDQ is a, previously validated, self-report instrument to measure gastrointestinal symptoms. Diagnosis of IBS was based on Rome II criteria. The IBS prevalence was significantly higher in asthmatics (62/150, 41.3%) than in subjects with other pulmonary disorders (29/130, 22.3%, P<0.001) and healthy ones (25/120, 20.8%, P<0.001). For all subjects studied, the prevalence of IBS was significantly higher in females (78/214, 36.4%) than in males (38/186, 20.4%, P<0.001). The IBS prevalence in asthmatic males was 29.5% vs. 15.2% in male patients with other pulmonary disorders (P=0.002) and 14.2% in male healthy subjects (P=0.002). The IBS prevalence in asthmatic females was 51.8% vs. 28.1% in females patients with other pulmonary disorders (P<0.001) and 26.5% in females healthy subjects (P<0.001). None of the asthma medications were associated with increased or decreased likelihood of IBS. We conclude that patients with bronchial asthma have an increased prevalence of IBS. Further studies are needed to clarify the potential pathogenetic mechanisms underlying the association between IBS and asthma.