The purpose of the paper was to investigate the usefulness of posturographic analysis in patients with rheumatoid arthritis (RA) and osteoarthritis (OA). RA is a chronic inflammatory disorder responsible for destruction of active and passive components of joints. It is the most common autoimmune disease, and the second most common form of arthritis after OA. OA is a chronic disorder characterized by irreversible changes in the joint structure developing with advancing age. Both diseases lead to the destruction of many parts of the motor system, cause pain, weakness, and damage of ligaments, muscles, bones, and articular cartilage. The etiology of the diseases remains unknown. In the present study, evaluation of body balance in the standing position was performed by means of Pro-Med force plate system. Three posturographic tests were applied: with eyes open, closed, and with the biofeedback--under conscious visual control of body movements. The following posturographic parameters were measured: the radius of sways, the developed area, and the total length of posturograms, and also two directional components of sways: the length of left-right (in frontal plane) and forward-backward (in sagittal plane) motions. The results demonstrate that the biofeedback test is most useful in the evaluation of instability in rheumatic patients; it is more powerful than the other posturographic tests evaluated.