The pendulum test, recognized as a reliable measure of spasticity, has been replaced in this study by a video-based two dimensional motion analysis system. Using twenty five patients with spasticity(21 males, 4 females; mean age 46.6 year-old) in their lower legs due to lesions affecting the central nervous system and twenty two persons without any evidence of hypertonia(all males; mean age 23.4 year-old), five parameters such as relaxation index(RI), amplitude ratio(AR), torque at maximal acceleration velocity, number of swing and swing time were obtained for the purpose of documenting the reliability of the video-based two dimensional motion analysis system for the evaluation of spasticity. The values of RI(P<0.05), AR(P<0.01), and swing time(P<0.05) in patients with spasticity were significantly lower than control, whereas the value of torque in patients was significantly higher than control(P<0.01). Spearman's correlation coefficients of the RI(r=+/-0.70894, P<0.001), AR(r=+/-0.71832, P<0.001), number of swing(r=+/-0.59037, P<0.05) and swing time(r=+/-0.59648, P<0.01) showed a statistically significant negative correlation with the modified Ashworth scale, whereas that of torque(r=0.59037, P<0.01) showed a significant positive correlation. In conclusion, a pendulum test using a video-based two dimensional motion analysis system is a simple, and a reliable method for the quantitative evaluation of spasticity.