For cases of extended necrotizing pancreatitis which involve the spread of infectious or hemorrhagic necrotic lesions to the retroperitoneal tissue, we recommend sequestrectomy and subsequent retroperitoneal lavage via the retroperitoneal access. For successful retroperitoneal lavage, as much liquefactive infectious necrotic tissue as possible should be removed from the retroperitoneal cavity during the operation. In addition, the necrotic cavity should be opened, adequately washed out, and catheters placed in the retroperitoneal cavity by retroperitoneal access. Although we have only applied this ideal technique in two patients so far, the details are presented herein. The significance of retroperitoneal lavage lies in the fact that it cleans the retroperitoneal foci of infection and necrosis, and that it eliminates the necrotic material, bacterial deposits, and biologically active substances produced after surgery. Ultimately, wound healing is markedly promoted, leading to improvement in the systemic condition.