The purpose of this study was to determine whether high-speed treadmill training improved the gait velocity of patients whose maximum walking speed was assumed to have reached a plateau level. The subjects included seven patients with hemiplegia after stroke. The high-speed treadmill training was performed as the maximum gait velocity of each patient was presumed to have reached a plateau level. The patients walked 20% faster than their maximum gait velocity of the day for 5 days (phase I). Then they walked 20% slower than maximum gait velocity of the day for 5 days, and they repeated the fast treadmill walking for further 5 days (phase II). Before phase I, mean maximum gait velocity of the day was 0.84 m/sec before phase I, 1.08 m/sec after phase I, and 1.24 m/sec after phase II. These results demonstrated that training at a speed 20% faster than the maximum gait velocity of the day on the treadmill for 5 days could further increase a patient's gait velocity.