During the 2-year period 1978-1979, a total of 2109 hip fractures (of the proximal end of the femur) occurred in Oslo. The age- and sex-specific annual incidence was the highest ever reported. A previous hip fracture had occurred in 13 per cent of the women and 6.8 per cent of the men. In 1979, a total of 5920 hip fractures was reported in Norway. Compared with Oslo, all other counties had a lower incidence. The number of fractures in Oslo was five times greater in 1982 compared with 1950. This increase cannot be explained only by the increasing number of elderly persons.