The post-isometric relaxation technique begins by placing the muscle in a stretched position. Then an isometric contraction is exerted against minimal resistance. Relaxation and then gentle stretch follow as the muscle releases. This technique was applied to tight, tender muscles that are commonly associated with musculoskeletal pain and was systematically tested on 351 muscle groups in 244 patients. The method produced immediate pain relief in 94%, lasting pain relief in 63%, as well as lasting relief of point tenderness in 23% of the sites treated. Patients who practiced autotherapy on a home program were more likely to realize lasting relief. Pain was relieved in both the muscle itself and at tender insertion points. The technique is useful in addition to, or in place of, local anesthetic injection or dry needling. These results confirm other observations that the increased tension of the affected muscles and the resulting pain and dysfunction are both relieved by restoring the full stretch length of the muscle.