Osteogenesis imperfecta is a connective tissue diathesis according to Follis.1He demonstrated poor embryologic transformation of primitive reticular fibers to mature collagen fibers of the connective tissues of various organs of the body. The organs generally involved are the bones, skin, fibrous coat of the eye, and internal ears. The connective tissues of bone membranes appear primitive so that bones formed by membranous ossification are defective. Multiple fractures of bones have been the predominant clinical abnormality.2 Each of the two cases of osteogenesis imperfecta congenita reported in here also had prominent connective-tissue fiber aberrations in the cardiovascular system, a finding not previously described. Report of Cases Case1.—The patient, a white male newborn, weighing 2,500 gm (5 lb 8 oz), had multiple fractures of the ribs and extremities, confirmed by a roentgenogram (Fig 1). The head had wide fontanelles and small wormian bones. The sclera was blue in