We studied the incidence of hip fractures in the county of Troms. This was compared with the incidence in a district of the city of Oslo. In both regions, the incidence increased almost exponentially with age both for men and for women. Since 1978, age-adjusted incidence has increased. This is most pronounced for men and for the county of Troms. In 1978 there was a marked difference between Oslo and Troms as regards risk of hip fracture. In 1989 this difference had diminished and persisted only among very old people. Risk factors other than postmenopausal and senile osteoporosis are discussed in an attempt to explain this development.