Objective: Some data suggest that the Manning criteria for diagnosis of the irritable bowel syndrome (IBS) are less reliable in men. This research aims to detect gender differences in the prevalence of individual diagnostic criteria in IBS patients. Design: One hundred and fifty-six IBS patients (26 males, 130 females) were asked about their bowel symptoms including the Manning and Rome criteria. Results: In the IBS group, 90.4% fulfilled the Manning criteria (91.5% females, 84.6% males), and 68.6% the Rome criteria (70.8% females and 57.7% males). The three pain-related criteria (pain relieved by defecation, pain followed by change in stool frequency or stool consistency) were similarly present in males and females. However, mucus, feeling of incomplete evacuation, and distension were found in 86 (66.2%), 78 (60%) and 72 (55.4%) of the women, compared to 10 (38%), 7 (26.9%) and 9 (36.9%) of the men (P<0.009, P<0.002 and P=0.053, respectively). Scybala, which are among the Rome criteria, were also less prevalent in males (7.7% vs. 29.2% (P<0.03)). Conclusion: Among IBS patients, pain-related Manning symptoms are similar in men and women, but mucus, incomplete evacuation, distension and scybala are less common in men. Less reporting of these symptoms by men may account for reduced clinical reliability of the Manning or Rome criteria in men and their apparent low prevalence of IBS.