Sever's injury (apophysitis calcanei) is considered to be the dominant cause of heel pain among children between 8 and 15 years. The traditional advice is to reduce and modify the level of physical activity. Recommended treatment in general is the same as for adults with Achilles tendon pain. The purpose of the study was to find out if insoles, of two different types, were effective in relieving heel pain in a group of boys (n=38) attending a Sports Medicine Clinic for heel pain diagnosed as Sever's injury. The type of insole was randomized, and self-assessed pain during physical activity in the treatment phase with insoles was compared with pain in the corresponding pre- and post-treatment phases without insoles. There were no other treatments added and the recommendations were to stay on the same activity level. All patients maintained their high level of physical activity throughout the study period. Significant pain reduction during physical activity when using insoles was found. Application of two different types of insoles without any immobilization, other treatment, or modification of sport activities results in significant pain relief in boys with Sever's injury.