BACKGROUND: Free tissue transfer to the lower extremity has become a well-established reconstructive modality. The purpose of this study was to develop a "subunit" approach to patients undergoing free tissue transfer for foot and ankle wounds to help further define subunit-specific functional and aesthetic operative goals. METHODS: The institutional review board approved this retrospective review of 161 patients who underwent free tissue transplantation for foot and ankle wounds between March 1, 1997, and February 28, 2007, at a single institution. Endpoints included flap-related complications, secondary surgery, time to ambulation, flap stability, and limb salvage. RESULTS: The most common types of wounds treated were trauma-related [n = 120 (75 percent)], diabetes-related [n = 24 (15 percent)], and oncologic defects [n = 8 (5 percent)]. Ten different donor sites were used for reconstruction, with the latissimus dorsi flap being the most common. The mean follow-up time was 26.9 months (range, 0.5 to 130 months). Mean time to ambulation was 3.1 months (range, 0.75 to 14 months). Overall, 11 percent of patients required revision surgery for flap instability at a mean time of 25.3 months after flap surgery. Wounds located over the heel (subunit 5) were most likely to develop instability (Fisher's exact test, p < 0.05). The overall 5-year limb salvage rate as determined by Kaplan-Meier analysis was 89 percent. CONCLUSIONS: The use of free tissue transplantation for treatment of foot and ankle wounds is associated with a high rate of limb salvage. Although a variety of flaps may be used, the application of the subunit principle can assist surgeons in designing flaps that will address subunit-specific functional and aesthetic concerns.