The usefulness of leaving lateral strips of the rectus abdominis muscle in place during a transverse rectus abdominis musculocutaneous (TRAM) flap procedure is questioned. Since textbooks do not agree on the course of the intercostal nerves in the rectus fascia and no precise description is given of the exact site of penetration of the nerves in the rectus muscle, six fresh cadavers were dissected. It has been observed that the nerves enter the deep face of the muscle in its middle portion. Lateral parts of the muscle are consequently denervated during a transverse rectus abdominis musculocutaneous flap, which preserves them. This has been confirmed by CT scan of the abdominal wall in 10 patients 2 to 37 months after a transverse rectus abdominis musculocutaneous flap. In these patients, a progressive fibrosis and disappearance of the remaining muscle could be demonstrated. It is concluded that a partial taking of the rectus abdominis muscle does not preserve its muscular function.