The hypothesis has been tested that postcholecystectomy common duct stones of the brown subtype are a consequence of three factors: bile infection, old age and previous sphincterotomy. It was found that: (i) 27 of 39 consecutive patients with recurrent common duct stones had brown stones. Nineteen of these 27 patients (70.3%) had previous sphincterotomy or sphincteroplasty: (ii) six of 15 patients with stone and bile analysis both at the time of cholecystectomy and at the second operation and who had sterile operative bile and non brown stones at the first operation, formed brown stones after T-tube drainage and after the onset of bile infection; (iii) patients with both intra and postoperative negative bile culture (n = 39 out of 137) had a lower mean age (50.5 years) and less frequently had a sphincterotomy than did individuals with a negative culture at operation, who subsequently had bile infection (n = 37; mean age 58.5 years; sphincterotomy in 88.8% of cases). In addition, in a follow up study of 105 patients with sphincterotomy and with sphincteroplasty (including ERCP or i.v. cholangiography in all cases), mean follow-up interval 6.1 years, 11.3 % of patients had brown recurrent common duct stones. It is suggested that, since brown recurrent common duct stones are secondary to bile stasis and infection and the duodenum is going to be colonized by bacteria with increasing age, sphincterotomy (and subsequent stricture), facilitating bile contamination and bacterial overgrowth, could be one of the major determinants of brown recurrent common duct stones (RCS) formation. In particular, more than 11% of the patients with a sphincterotomy are going to form in the future RCS of the brown subtype.