1. Forty new cases of cleidocranial dysostosis are presented in this genetic and roentgenologic evaluation. 2. Abnormalities observed previously in the disease are assessed including the following hallmark patterns: unossified fontanelles; posterior wedging of the thoracic vertebrae; delayed ossification of the pubic bones; and pointing of the terminal phalangeal tufts. 3. New aspects of the disorder recognized in this study include: distinctive segmental calvarial thickening in the temporal and occipital bones; right clavicular selectivity; high incidence of spondylolysis of the lumbar vertebrae; and characteristic lateral notching of the capital femoral epiphysis. 4. Cephalopelvic disproportion is emphasized as a potential cause of severe dystocia, necessitating cesarean sections in 5 of 14 parous women with the disorder.