Five cases of stress fracture of the patella in athletes are presented. Four of these occurred transversally in the lower part and one longitudinally in the lateral part of the patella. Three of the patients were females (endurance runner, high jumper, and orienteerer) and two males (volleyball and soccer player). The diagnosis was made 2-8 months from the onset of the symptoms. Conservative treatment was successful in only one patient; all others were treated surgically, with good end result. Drilling of the fracture line was performed twice with metal wire cerclage fixation, excision of the lateral fragment was carried out once, and a bone graft with K wires and cerclage compression (tension band) was performed once. In all cases the patellar retinaculum was intact, indicating a stress injury. Stress fracture of the patella is a rare overuse injury, and therefore difficulties and delays in the diagnosis and treatment may occur. In cases with delayed diagnosis we recommend operative treatment.