Thirteen cases of lengthening of short tubular bone by gradual axial distraction using an unilateral external fixator(Orthofix M-100, Orthofix CP0089) are reported. This study aims to prove effective- ness of gradual distraction for lengthening of short tubular bone and usefulness of the newly designed external fixator. Nine patients had brachymetatarsia and four brachymetacarpia. The etiology was consisted of post-traumatic physeal injury in two and congenital in eleven cases. The average amount of lengthening was 14.5mm(37.0%) in metacarpal bone, and 17.3mm(37.5%) in metatarsal. Complications were angular deformity in 3, pin loosening in 2 cases, and premature consolidation, nonunion and pin site infection in one case, respectively. Cosmetical and functional satisfactory results were obtained in all cases. We believe that callotasis is effective for short tubular bone lengthening. Also we confirmed the newly designed external fixa- tor(Orthofix CP0089) useful.