There are such marked variations in the vascular anatomy of the nutrient vessels in medial and posterior upper arm flaps, that widespread usage of these flaps has been delayed. The authors have evaluated both medial and posterior upper arm flaps and have concentrated on the status of the skin perforators. Both types of flaps were considered for use as free transfers in 25 cases; island flaps were successfully elevated in 22 patients (11 medial and 11 posterior flaps). Because of the lack of suitable perforating vessels, this solution was abandoned in three patients. Perforators in both areas were found in 44 percent of the cases, in one or the other area in 44 percent, and not at all in 12 percent of the cases. Using the determination of perforators, the success rate of free-flap transfers from the medial and posterior upper arm increased from 64 and 68 percent, respectively, to 88 percent. When harvesting a flap from the medial or posterior upper arm, the risks attending questions of vascular stability in free-flap transfer, may be overcome by clinician experience.