Body sway in patients standing with eyes closed was observed by tilting the plate toward the front, back, left, and right. Patients with equilibrium dysfunction produced a specific body sway under these conditions. It is shown that merely standing on the flat plate does not always show a specific pattern even in patients with equilibrium dysfunction. However, for subjects standing on the tilting plate, it is possible to discriminate equilibrium disorders from normals. Eight directional display and a power spectrum of body sway are useful for the diagnosis of equilibrium dysfunction. Abnormal subjects show a peculiar pattern in the radar chart display of displacement, and the power spectrum of body movement does not obey the rule of 1/f fluctuation. >