An anatomic and topographic study of the lateral upper arm free flap for the clinical use in reconstruction. Defects of the laryngopharynx and the oral cavity after cancer ablation are increasingly reconstructed by free microvascular anastomosed tissue transfer. Besides the jejunum transplant we use the free radial forearm flap frequently. This flap is suitable for restoring intraoral and pharyngeal integrity. Major disadvantages are the requirement of a skin graft to obtain wound closure and the cosmetic deformity. The lateral upper arm free flap is intended as alternative method for the fasciocutaneus tissue transfer. Based on our dissection of ten cadavers we demonstrate the anatomy of the flap, the harvesting technique, and present data of vascular pedicle length, vessel calibers, and flap size. The vessel calibers of the profound brachial artery (X = 2.5 mm) and its terminal branch, the posterior radial collateral artery (X = 1.8 mm), are comparable to the radial artery. The pedicle length can be extended up to 13 cm by using a lateral approach. The subcutaneous tissue volume was 1.3 cm in average, and compared to the radial flap rather thick. Because of his bulky and strong fascia the lateral arm flap seems to be useful as a fascia-fat flap in facial augmentation or as a fascia flap in soft tissue reconstruction. Disadvantageous are the difficult dissection technique and the loss of sensitivity on the lateral aspect of the forearm. Where a fasciocutaneous flap is indicated, we prefer the radial forearm flap.