The American Orthopedic Foot and Ankle Society recommends at least six months of nonsurgical treatment before considering surgical intervention for painful heel syndrome. Achilles tendon stretching exercises are consistently reported to be one of the more effective nonsurgical modalities for treatment of painful heel syndrome. However, the optimal duration and frequency of the exercises has not been reported. The purpose of this study was to evaluate and compare the effectiveness of sustained and intermittent Achilles tendon stretching for the relief of pain associated with painful heel syndrome. This prospective, randomized, blinded study was performed from May 1997 to July 2000. A total of 94 people (122 affected feet) fit the inclusion criterion and agreed initially to participate in a treatment study group. To achieve our purpose, study participants were randomized into two stretching groups. One group performed sustained Achilles tendon stretches (three minutes, three times daily), the other performed intermittent stretches (five sets, 20 seconds each, two times daily). Participants were evaluated once a month for a period of four months subsequent to diagnosis. At each monthly visit, participants completed subjective questionnaires about their pain. Also, a physical therapist measured each participant's Achilles tendon flexibility. The study determined that both sustained and intermittent Achilles tendon stretching exercises increase Achilles tendon flexibility. This increase in flexibility correlated with a decrease in pain. There was no significant difference in outcome between the sustained and intermittent stretching groups. The data suggest that both sustained and intermittent Achilles tendon stretching exercises were effective nonsurgical treatments for painful heel syndrome.