We investigated the effects of direct gradual lengthening of the distal stump of a peripheral nerve and subsequent nerve regeneration in rats. A segment 10 mm long was resected from rat sciatic nerve. The distal nerve stump was fixed to a ring and pulled directly at a rate of 1 mm/day using an original external nerve distraction device. After distraction for 10, 15, and 20 days, the lengthened nerves were evaluated macroscopically and immunocytochemically. At day 20, the mean (SD) distances from the ring to the 3 mm and 6 mm distal part, which were marked with sutures on the epineurium, were 7 (0.5) mm and 12.1 (0.5) mm, respectively, and the number of Schwann cells in the lengthening group had increased to twice that of control group. The distal stump of a peripheral nerve including the epineurium, endoneurium, and proliferation of Schwann cells can be lengthened directly. This method also made it possible to lengthen the nerve stump longitudinally and to control both the rate and distance. We think that this method may be used in the treatment of peripheral nerve injury.