In a series of 151 tibial stress fractures in athletes and joggers, seven were located at the mid-third of the diaphysis. The diagnosis was made radiographically several months after the onset of symptoms; a transverse fissure line or gap was noted in the middle of the hypertrophied anterior tibial cortex. Histologic examination of a biopsy of the fracture line showed features resembling pseudoarthrosis. All the patients returned to physical activities.