The authors describe a new technique for reconstruction of the thumb after amputation through the proximal phalanx. Bipolar lengthening is a combination of first web deepening by an Ostrowski flap and a distal lengthening by a free vascularized compound transfer of pulp, nail, and bone harvested longitudinally from the distal phalanx of the great toe. Seven cases have been reviewed by an independent observer after a mean follow-up of 46 months. There were no technical failures. The mean static 2-point discrimination was 6.3 mm, and the Semmes-Weinstein monofilament testing was identical to that of the contralateral side in four patients and increased in the other three. After correction for hand dominance, grip strength was 89 percent of that of the contralateral side, and pinch strength was 81 percent of that of the contralateral side. First web span was symmetric in four patients and diminished in the other three. The bipolar technique creates a short thumb, which avoids exposing the thumb to trauma when making a fist, without limiting first web span.