Fractures of the proximal fifth metatarsal can be divided into two distinct groups based on anatomical location and clinical course. Fractures of the tuberosity often heal well with nonoperative treatment, whereas fractures occurring in the proximal diaphysis (up to 1.5 cm distal to the tuberosity) have significantly increased risk for delayed union or nonunion. It is the purpose of this paper to describe the intraosseous vascular anatomy of the fifth metatarsal, and the clinical implications for basilar fracture healing. Ten fresh-frozen amputation or cadaver specimens were studied following arterial injection with India ink or barium sulfate suspension. The intraosseous blood supply to the fifth metatarsal tuberosity arose from numerous metaphyseal vessels penetrating the nonarticular surfaces of the tuberosity in a random, radiate pattern. The blood supply to the proximal diaphysis was derived primarily from the nutrient artery, which gave rise to longitudinal intramedullary branches. The arterial supply to the tuberosity joined the supply of the proximal diaphysis in the area just distal to the tuberosity, corresponding to the region of poor prognosis for fracture healing. This suggests that a relative lack of blood supply following a proximal diaphyseal fracture may contribute to delayed union and nonunion.