The Canadian Multicenter Osteoporosis Study is a large population-based prospective study of osteoporosis in the Canadian population. The study involves 9424 subjects, both male and female, from nine centers and seven regions of Canada. Each subject completed an extensive interview to obtain medical, demographic and lifestyle information, and was examined by dual-energy X-ray absorptiometry of the spine and hip, ultrasound of the heel and, for subjects over 50 years of age, lateral spine radiographs. Spinal morphometry of the initial radiographs was performed to determine the prevalence of vertebral deformity. A method is utilized to extract reference norms for vertebral shape from a subset of the population data, which is then used to categorize any deformity within the whole data set. Using 3 standard deviations (SD) as a limit of normality', the male prevalence of 21.5% was similar to the female prevalence of 23.5%. Using 4 SD this reduced to 7.3% and 9.3% respectively. The younger men (50-59 years) showed a higher prevalence of deformity than the women and a lower increase of prevalence with age. In the older age group (over 80 years) the female prevalence of 45% compared with 36% for the men using 3 SD (grade 1) to define the limit of normality. The female group presented with more severe deformities on average than the male group. This continuing study will provide longitudinal information regarding the development of osteoporosis and associated risk factors which will eventually be of use to develop public health policies.