We studied the fracture rate as a function of age in 45 women and 20 men with osteogenesis imperfecta. In each variant of the disorder, the fracture rate in women peaked in childhood, declined in adolescence, and rose again after the menopause. In contrast, the fracture rate in men remained low after adolescence. After the menopause women were vulnerable to crush fractures of the spine as well as fractures of the long bones. We conclude that the increased fracture rate after the menopause in women with osteogenesis imperfecta reflects the superimposition of the effects of age-related bone loss on those of the defective collagen structure of osteogenesis imperfecta, and that hormone-replacement therapy may be specifically indicated in this group of patients from the time of the menopause. We also suggest that osteogenesis imperfecta should be included in the differential diagnosis of women presenting with crush fractures of the spine.