PURPOSE: To evaluate radiation therapy (RT) to treat refractory pain in plantar heel spur. MATERIALS AND METHODS: From 1984 to 1994, 141 patients with refractory painful plantar heel spur (170 heels, because of bilateral disease) underwent RT. Quantitative criteria were used to evaluate heel pain and ankle function prior to RT, 6-12 weeks after RT, and at last follow-up (median, 4 years). Patients were divided into three treatment groups: group A (n = 72 heels [two courses, 1.0-Gy fractions, 12-Gy total RT dosel), group B1 (n = 50 heels [one course, 0.3-Gy fractions, 3-Gy total dose]), and group B2 (n = 48 heels [one course, 0.5-Gy fractions, 5-Gy total dose]). RESULTS: At last follow-up, complete pain relief was achieved in 48 (67%) of 72 group A heels and in 71 (72%) of 98 group B heels. Statistically significant (P < .05) differences between groups were found for insufficient pain relief (<80%) in patients in whom the response time after RT was longer than 4 weeks or in whom pain recurred during follow-up. The best results were achieved with the 5-Gy total RT dose (P < .05). Prognostic factors for complete pain relief were acute pain and short duration of pain prior to RT. The prognostic factor for insufficient pain relief was total RT dose. CONCLUSION: Refractory heel pain is effectively treated with RT, which should be considered a primary treatment approach rather than a last resort.