Restoration of structure, function, and sensation are critical after trauma or tumor resection of the hand. Thorough debridement, reconstruction of functional structures, and immediate soft tissue coverage are most effectively performed in a single stage within approximately 24 hours of the injury. Skin flaps provide robust, pliable, and cosmetically appropriate tissue that is not prone to contracture and that facilitates secondary reconstructive work. Muscle flaps retain indications for complex defects with substantial initial contamination or dead space, or for reanimation. In this article, the indications, options, and surgical techniques for free muscle flap reconstruction of upper limb defects are reviewed.