1. A case is described of fatigue fractures occurring in the lowest thirds of the right tibia and fibula simultaneously.

2. The fibular fracture was a runner's fracture.

3. The tibial fracture was ascribed to the application of a below-knee walking plaster to treat the fibular lesion.

4. Both fractures were slow in uniting.

5. The fractures occurred in a rapidly growing youth but no clinical evidence of an endocrine dysfunction was found.