Three adults with osteogenesis imperfecta and associated cardiovascular lesions are reported. Two presented with aortic insufficiency due to dilatation of the aortic root for which none of the usual causes is apparent. The third patient was found to have lesions involving pulmonary, aortic, and mitral valves in addition to microscopic changes in the pulmonary artery and aorta. It is suggested that in osteogenesis imperfecta, as in other heritable disorders of connective tissue, cardiovascular defects may become apparent after the passage of time and play a dominant role in the natural history of the disease process.