A systematic review included 17 studies with a total of 1 363 subjects with irritable bowel syndrome (IBS). Fibre, in general, was effective in the relief of global IBS symptoms (RR 1.33; 95% CI 1.19–1.50). IBS patients with constipation may receive benefit from fibre treatment (RR 1.56; 95% CI 1.21–2.02), but there was no evidence that fibre was effective in the relief of abdominal pain in irritable bowel syndrome. Soluble fibre (psyllium, ispaghula, calcium polycarbophil; 9 studies) showed significant improvement (RR 1.55; 95% CI 1.35–1.78), whereas insoluble fibre (corn, wheat, bran; 8 studies), in some cases, worsened the clinical outcome, but there was no significant difference compared with placebo (RR 0.89; 95% CI 0.72–1.11).