Background: We have shown that bran exacerbates irritable bowel syndrome symptoms in a large proportion of secondary-care patients. However, it is unknown if this also happens in primary-care or whether a better response to bran occurs, leading to bran failures being selected for referral to the specialist. Aims: To assess the response to bran in primary-care irritable bowel syndrome comparing it to that obtained in secondary-care. Patients and methods: One hundred consecutive primary-care irritable bowel syndrome patients were asked how bran or soluble fibre products affected their symptoms. Results: Bran improved symptoms in 27% of primary-care and 10% of secondary-care patients (p <0.01) and exacerbated symptoms in 22% of primary-care and 55% of secondary-care patients (p <0.001). Fifty-one percent of primary-care and 33% of secondary-care patients reported no change with bran. In primary-care, proprietary fibre led to improvement in 25%, deterioration in 19% and no change in 56% which was not significantly different to secondary-care. Conclusion: Although not especially effective in primary-care irritable bowel syndrome patients, bran does not cause so many problems and is more helpful than in secondary-care. The effects of soluble fibre are similar in both primary-care and secondary-care. This study highlights the problem of extrapolating the response to treatment in irritable bowel syndrome from different care settings. © 2006 Editrice Gastroenterologica Italiana S.r.l.