The purpose of this study was to investigate effects of the long-term high-frequency transcutaneous electrical nerve stimulation(TENS) on the spasticity and the balance in chronic stroke patients. Twenty-six subjects with spasticity over lower limbs were allocated randomly into two groups under standard rehabilitation: (1) TENS group, (2) placebo-TENS group. TENS stimulation was applied on the both the gastrocnemius for 30 minutes, 5 days a week for 4 weeks(100 Hz, 0.25 ms, 2 times sensory threshold). The Modified Ashworth Scale(MAS) and Hand-held manual muscle tester were used to assess the ankle plantarflexor spasticity. Balance function under three conditions was measured by using force-plate and the amount of postural sway was assessed; in (1) the condition of standing with eyes opened, (2) with eyes closed and (3) the condition of standing on unstable surface with eyes opened. Both groups showed significant improvement in spasticity and balance function after treatment for 4 weeks(p<.05). Especially, TENS group showed a significant reduction of spasticity compared to placebo-TENS group(p<.05). These results suggested that additional stimulation of a long-term high-frequency TENS to standard rehabilitation induced an improved balance function and a spasticity reduction. The long-term application of high-frequency TENS will be an effective intervention for reducing spasticity and increasing balance ability in the chronic stroke patients.