One hundred and twenty-nine stress fractures of the os calcis were observed in a series of 300 stress fractures in 231 patients. Several reasons may be attributed to the infrequent diagnosis of stress fractures in the general population, including failure to obtain roentgenographic studies of a painful site because of no history of a specific traumatic event, and failure to recognize a stress fracture, even though roentgenographic studies were performed, because most physicans are unfamiliar with stress fractures. The treatment of these calcaneal stress fracture included prohibition of crawling, stooping, running, jumping, and prolonged standing or marching. Casting was not done. This therapeutic regimen was carried out for a period of 4 weeks. Most of these patients were asymptomatic within 3 weeks and returned to full activity following the above described treatment. The treatment of any stress fracture is conservative while the treatment of osteosarcoma includes radical surgery or X-ray therapy. Osteoid-osteomas are treated by local excision. An accurate diagnosis of a slerotic bony lesion is imperative to avoid serious therapeutic mistakes.