In this article, the author focuses on functioning free muscle transplantation (FFMT), an advanced microneurovascular technique indicated in patients who have an advanced injury with a major brachial muscle or muscle group loss or denervation and in whom no locally available or ideal musculotendinous donor unit exists. FFMTs have been successfully applied clinically in cases involving adult brachial plexus palsy, obstetric brachial plexus palsy, facial palsy, severe Volkmann’s ischemia, and severe crushing and traction injuries of the forearm or arm with major muscle loss. As the author notes, FFMT is a new challenge for the reconstructive surgeon. He outlines the eight major principles for nerve transfer with FFMT, basing his conclusions on the more than 333 patients who received FFMT between 1995 and 2005 in his hospital.