Joint mobilization is a common technique used to restore joint motion; however, documentation of its effectiveness is lacking. The purpose of this study was to determine if joint mobilization is effective in counteracting joint stiffness and decreased active range of motion of the metacarpal-phalangeal joint. It was hypothesized that there would be a significant increase in range of motion in those patients who received joint mobilization. Eighteen subjects who had been immobilized for the treatment of metacarpal fractures were randomly assigned to a treatment group that received joint mobilization or a control group that received no treatment. Measurements of active range of motion and torque range of motion prior to and after treatment/rest sessions were obtained for three sessions over a 1 week period. Analyses of variance were performed on the mean changes in excursion between groups and across sessions. The joint mobilization resulted in a significantly greater increase in excursion for subjects in the treatment group over subjects in the control group (p < 0.05). Joint mobilization does appear to be able to counteract the effects of immobilization and alter joint mechanics. J Orthop Sports Phys Ther 1992;16(1):30-36.