Thirty large incisional abdominal hernias (myoaponeurotic defects greater than 10 centimeters) were successfully repaired by a technique of incisional hernioplasty which implants a large Mersilene (polyester fiber) prosthesis in the space between the abdominal muscles and the peritoneum. The prosthesis extends far beyond the borders of the myoaponeurotic defect, and is solidly held in place by intra-abdominal pressure and later by fibrous ingrowth. The prosthesis protects against recurrence in two ways. First, it prevents peritoneal eventration by adhering to the visceral sac and rendering it indistensible. Second, the prosthesis unites and consolidates the abdominal wall. Consequently, the procedure uniquely exploits the very force which caused the hernia to prevent a recurrence. A prosthesis of Mersilene is essential for success because it is supple and elastic enough to conform freely to the curvatures of the visceral sac, has the necessary grainy texture to grip the peritoneum and prevent slippage and is reactive enough to induce a rapid fibroblastic response to ensure fixation.