A 35-year-old man underwent revascularization of a thumb transected through the base of the proximal phalanx after sharp division of all structures except a bridge of dorsal skin 1 cm wide. The digit survived. Avascular necrosis of the bone of the distal segment of the proximal phalanx was evident at 4 weeks and maximal at 9. Avascular necrosis did not occur in the distal phalanx. Roentgenographic changes indicated revascularization initially at the distal end of the phalanx, progressing proximally. Revascularization was first evident subperiosteally and progressed centrally; it was complete at 31 weeks. Fracture healing was delayed—evident at 17 weeks and complete at 27 weeks after injury. Avascular necrosis of bone may be the cause of delayed union or nonunion of bone cited in recent long-term reviews of successfully replanted digits. Measures should be taken to monitor, minimize, and compensate for this complication.