Duodenal perforations occur in 0.4-1% of endoscopic manoeuvres. In cases of periampullary injury, the best therapeutic approach is still controversial. Generally, the first treatment will be conservative, but in some patients large retroperitoneal infections requiring surgical treatment develop. Six patients, referred to our unit for extensive retroperitoneal collections and unstable septic conditions as a consequence of periampullary duodenal perforation during ERCP, were treated by right posterior laparostomy with twelfth rib resection. The septic process was treated efficaciously by the open posterior approach that favoured the spontaneous closure of the duodenal leak after a mean period of 14.5 +/- 5.2 days. No hospital deaths or major complications were recorded. Late incisional hernia developed in one case. The technique of posterior laparostomy with twelfth rib resection permits adequate debridement and drainage of both the upper and lower parts of the retroperitoneal space involved in infection after periampullary duodenal perforations. The good control of both the retroperitoneal septic process and the duodenal secretions facilitates the spontaneous closure of the duodenal leak, thus avoiding the risk of more complex and dangerous procedures.