Six symptoms of Manning et al are widely used in clinical practice to diagnose irritable bowel syndrome (IBS). We studied 123 patients to evaluate the diagnostic value of Manning's criteria, using a preformed bowel symptom questionnaire which included these six symptoms. This study included 65 patients with IBS, 35 patients with non-ulcer dyspepsia, 23 patients with organic diseases of colon and 45 healthy controls. Sensitivity of presence of three or more symptoms of Manning's criteria discriminating irritable bowel syndrome from all other groups was 66.1%. Manning's criteria discriminated irritable bowel syndrome from organic diseases of colon with specificity and positive predictive value of 66.9% and 82.6%. When irritable bowel syndrome was compared with non-ulcer dyspepsia and healthy controls, specificities of Manning's criteria were 91.4% and 93.3% and positive predictive values 93.4% and 93.4% respectively.