In brief: To compare infrared thermography, radionuclide bone scanning, and routine x-ray in diagnosis, a prospective blind study was conducted on 17 athletes (ten men, seven women) who had exertional leg pain compatible with stress fracture. The athletes with 'hot' patterns were unable to resume their original activity, while those with 'cold' patterns were able to resume activity. Additionally, specific soft-tissue syndromes were identified. The data indicate that thermography may be an accurate, noninvasive new way to distinguish stress fracture from other causes of shinsplint syndromes in runners. Applied repeatedly, this technique could be used to follow the course of bone healing, permitting the earliest safe return to activity.