In order to preserve the anal function after ano-perianal skin excision for malignancy, we have reconstructed a deep, symmetrical natal cleft using a V-Y advancement of bilateral gluteus maximus musculocutaneous flaps thinned medially and sutured to the ooccyx, anococcygeal ligament and the central tendon of the perineum. This technique was applied in three cases of Bowen's disease and two cases of Paget's disease. In all five cases, postoperative anal functions such as comfortable defecation and sensation, were well preserved, the perianal skin and underwear stayed clean, and there was no disturbance of walking or exercise.