A vascularized bone segment of the ulna together with a posterior interosseous fasciocutaneous flap is harvested, including a cuff of the extensor pollicis longus muscle, The authors treated five male patients with metacarpal bone and soft-tissue defects of the hand using a distally based island osteocutaneous posterior interosseous flap. Their ages at the time of surgery ranged front 15 to 37 years (mean, 24 years). The bone defects were in the first metacarpal in three cases, the fourth metacarpal in one, and the fifth metacarpal in one. The length of the donated ulna ranged from 3 to 7 cm (mean, 5 cm). The follow-up period ranged front 5 to 92 months (mean, 39 months). All flaps survived completely. The posterior interosseous flap provides thin skin of good texture, together with vascularized bone, for a one-stage reconstruction of the metacarpal bone and soft-tissue defects in the hand.