Transplanted autogenous muscles were electrophysiologically studied in 2 patients with forearm crush injury. Only fibrillation action potentials and positive sharp waves were seen at 1 month after the operation. Low-amplitude and short-duration muscular unit potentials (MUPs) appeared at 3 months and high-amplitude, long-duration and polyphasic MUPs were frequently seen at 6–7 months after the transplantation. The distal latencies of the evoked motor responses were gradually shortened from time to time and eventually became normal at about 1 year after the grafting. The mean consecutive difference became normal at about 6 months after the normalization of the distal latencies. We conclude that the motor endplate is functionally completed at about half a year after the completion of the myelination of the grafted nerv