The Petersen or retroanastomotic Hernia, as shown in the first description by Petersen in 1900. is a herniation of either afferent or efferent limb of a gastrojejunostomy through the defect behind the anastomosis. This is a report of 2 cases of retroanastomotic Hernia with review of literature.The first Case occurred in the immediate Post-operative period and the second case 3 months post operatively. The purpose of this report is to reallert surgeons to this iatrogenic Hernia and outline the pathophysiology and preventive measure of the disease.