Stress fractures in athletes usually heal well with merely rest and conservative treatment. It has been estimated that in Finland 400-500 athletic stress fractures occur annually per year. In sports clinic series stress fractures comprise 3.3 to 4.6 per cent of all overuse injuries. Delayed and non-union have been reported to occur in athletes quite often, up to 10 per cent of athletic stress fractures in Finland. The reason is on the one hand delayed diagnosis due to late consultation of expert physicians, and on the other hand too short a rest from hard physical activity. Delayed and non-union are most often seen in the hallux sesamoids, mid-tibial staft, base of fifth metatarsal, tarsal navicular and olecranon. The pars articularis of the fourth and fifth lumbar vertebra is a site of stress fracture and spondylolysis. In this report the diagnosis, symptoms and findings as well as the operative treatment of these overuse injuries is discussed.