We studied the vascular relationship of the lateral arm flap to triceps tendon and muscle in 16 dissected cadaver arms. We designed composite lateral arm free flaps containing fasciocutaneous components, triceps muscle, and/or triceps tendon. Vascular communication between the lateral arm fascia and triceps tendon was negligible. In contrast, a mean of 3.6 vessels passed through triceps muscle from the posterior radial collateral artery to the harvested triceps tendon; in each dissection at least 1 vessel entered the proximal 5 cm and 1 vessel entered the distal 5 cm of harvested tendon. Methylene blue injections confirmed that perfusion of the triceps tendon was through triceps muscle and not through lateral arm fascia. We used the composite lateral arm free flap in 6 patients, 3 with triceps muscle and 3 with triceps tendon. Baltimore Therapeutic Evaluation testing in those patients where triceps tendon was harvested showed no deficit in elbow extension. Complete coverage of composite defects was achieved with a single surgical procedure in all patients.