We report a prospective study of the incidence of fractures in the adult population of Edinburgh, related to age and gender. Over a two-year period, 15,293 adults, 7428 males and 7865 females, sustained a fracture, and 5208 (34.0%) required admission. Between 15 and 49 years of age, males were 2.9 times more likely to sustain a fracture than females (95% CI 2.7 to 3.1). Over the age of 60 years, females were 2.3 times more likely to sustain a fracture than males (95% CI 2.1 to 2.4). There were three main peaks of fracture distribution: the first was in young adult males, the second was in elderly patients of both genders, mainly in metaphyseal bone such as the proximal femur, although diaphyseal fractures also showed an increase in incidence. The third increase in the incidence of fractures, especially of the wrist, was seen to start at 40 years of age in women. Our study has also shown that 'osteoporotic' fractures became evident in women earlier than expected, and that they were not entirely a postmenopausal phenomenon.