Treadmill locomotion has become a popular means of indoor exercise. Immediately after stepping off a treadmill following several minutes of exercise, individuals often feel as if the floor on which they are standing carries them forward. After natural running, similar sensations do not occur in healthy subjects.This study was undertaken to explore the nature of impaired postural stability following treadmill exercise. Postural sway was measured in 13 healthy subjects (11 males and 2 females; mean age 21.5 years) after walking with eyes open on a standard treadmill exerciser. The speed of walking was set at 5km/hr, and locomotion was maintained for 2, 4, 8, 16 minutes respectively. The postural sway response was characterized by systematic forward displacement followed by gradual decay to baseline and was accom-panied by perception of motion.Fore back postural sway range (FBPSR) after treadmill walking was significantly greater than FBPSR before treadmill walking. For 2, 4, and 8 minutes of treadmill walking, FBPSR after treadmill walking was greater when the walking time was longer. But for 16 minutes of treadmill walking, FBPSR after treadmill walking was smaller than that after 8 minutes of treadmill walking. For all treadmill walking perception of motion was greater when the walking time was longer.We concluded that treadmill locomotion may cause a visual somatosensory/motor conflict and recalibration of visuomotor control systems may be responsible for the sensation of motion after treadmill walking.