Stress fractures are bone fractures, in most cases at the lower extremities, caused by overload. Spondylolysis and -listhesis can be considered as stress fractures, too. During the past 10 years, 67 female and male athletes with stress fractures were treated and followed up until full ability to practice sports was achieved again. Bone scan (technetium 99) and nuclear resonance imaging MRI are devices for an early and exact diagnosis. Stress fractures mostly occur to runners. Conservative treatment includes a training-free interval with painlessness as the most important criteria. Only in rare cases immobilization or surgical treatment are necessary. As prophylaxis it is important to advice the athletes not to ignore overload pain.