Objective To investigate the role of oestrogen receptors and enteric mast cells in the pathogenesis of irritable bowel syndrome (IBS) . Methods Biopsies from 59 patients with IBS and 24 control subjects were analyzed blindly for the number of mast cell ( MC ) , estrogen receptors and progestogen receptors in terminal ileum , caecum and descending colon (DC). Immunohistochemical methods were used to detect the estrogen receptors (ER) , progestogen receptors (PR) and MC. And double Immunohistochemical staining was used to manifest the expression of oestrogen receptors in intestinal MC. Results The cells positive for ER were morphologically similar to the MC (R = 0. 884, P