Background: We tried to understand whether or not there is a significant relationship between irritable bowel syndrome (IBS) and smoking.& para;& para;Method: IBS is diagnosed according to Rome II criteria in the absence of red flag symptoms.& para;& para;Results: One hundred and four patients with IBS and 104 controls were studied. Interestingly, 78.8% (82 patients) of IBS patients were female with a mean age of 51.2 +/- 9.9 (29-70) years. Prevalence of smoking was significantly higher in cases with IBS (29.8% versus 11.5%, p<0.001). Similarly, prevalences of hyperbetalipoproteinemia, hypertriglyceridemia, and dyslipidemia were higher in cases with IBS but the difference was significant just for hypertriglyceridemia (26.9% versus 16.3%, p<0.01) probably due to the small sample size of the study. On the other hand, mean body mass index (BMI) and prevalences of hypertension (HT) and diabetes mellitus (DM) were all lower in cases with IBS but the difference was significant just for HT (10.5% versus 26.9%, p<0.001) probably due to the small sample size of the study, again.& para;& para;Conclusion: Although IBS may have a complex mechanism with a higher prevalence in females, smoking may be one of the several causes of IBS by causing avascular endothelial inflammation all over the body. The disseminated inflammation may be the cause of lower BMI and associated lower prevalences of HT and DM in the IBS cases. On the other hand, higher prevalences of hyperbetalipoproteinemia, hypertriglyceridemia, and dyslipidemia in cases with IBS may actually indicate their roles as acute phase reactants in smokers in the body.