Two infants with the Hanhart syndrome, i.e. micrognathia, microglossia, terminal deficiency of all limbs and imperforate anus in one, were dissected and studied in detail. The interrelationships of the muscular and skeletal defects suggested that they were the result of incomplete rather than abnormal morphogenesis. We speculate that the oral and limb abnormalities resulted from deficient mesodermal proliferation caused by disturbances in the ectodermal-mesodermal interactions beginning about the 4th week of development. The imperforate anus may also relate to the proposed defect.