With regard to the motions of standing up from and sitting down on a chair, and standing quietly for thirty seconds, forty normal adults (ten young males, ten young females, ten elderly males and ten elderly females) and ten hemiparetics were compared by use of a force plate and an electrogoniometer. The hemiparetics had the following characteristics: (1) A long time was required for stabilization of sway at the center of force (C.O.F.) when standing up. (2) The C. O. F. was located to the back and deviated primarily to the sound leg, and the grade of sway was greatest during quiet standing. (3) Vertical 8 Hz fluctuation in quiet standing was seen in all cases, while in sitting down 3-4 Hz were recorded. (4) The motion time in standing up and sitting down was prolonged. (5) Long periods of initial knee flexion existed just before the knee extension in standing. (6) A broad lateral sway of C. O. F. was recorded in the standing movement. Among the normal groups, the following characteristics were noted: (1) The young stand up more rapidly. (2) The elderly needed more time to stabilize the antero-posterior sway in the standing up motion. (3) The C. O. F. of males was located more anteriorly than that of females. (4) The grade of sway in quiet standing was greater in females than in males. (5) In young males, the standing up time was shorter than the sitting down time, while in young females the situation was reversed.(ABSTRACT TRUNCATED AT 250 WORDS)