A fatigue or stress fractures is one in which there is no initial overt break in bone continuity. Rather, there is a gradual alteration in bone architecture as a result of repeated stress. The stresses are submaxmum and usually are the result of unaccustomed activity. If continued, they may eventually result in a complete fracture. Fatigue fractures have been described in almost every bone in the body, but they are more common in the bones of the lower extremities. Fatigue fractures are commonly seen in military personnel, especially at basic training center, and have been noted in athletes, ballet dancers, laborers, and even pregnant women. The following clinical results were shown by analysis of 57 cases of stress fractures experienced in the Department of Orthopaedic Surgery, Capital Armed Forces General Hospital from Jan. 1978 to Sep. 1979. 1. In 57 fatigue tractures in military recruits, 48 were in the tibial shaft and 9 were in the fibula. 2. The main cause of the fatigue fractures was running on hard roads, and the other causes were marching on hard surfaces, playing football, and long jumping. 3. The site of predilection in the tibia was the proximal one third of the shaft, occurring in 35 (72.9%) of the cases. In the fibula the junction of the upper and middle thirds was most frequently affected, occurring in 4 (44.4%) of the cases. 4. Most of the tibial and fibular fatigue fractures were grade I (40 cases among 57), showing periosteal reaction only on one or two cortices. 5. All soldiers were treated by immediate stoppage of physical activity, with no plaster immobilization or non weight bearing.