In the past year it has been my great privilege to examine a number of Mongolian defectives at Waverley, Mass., at the invitation of Dr. Walter E. Fernald. The case reports, complete clinical data, biochemical findings and the result of treatment on an endocrinologic basis will be the substance of a later communication by Dr. Fernald and myself. I desire to make at this time a preliminary publication of the findings of the roentgenologic examination of many of the skulls for the reason that it may stimulate the making of such examinations in many centers with possible corroboration of my findings. Futher-more, if necropsy material is available, a special effort might be made, on the basis of the sellar changes shown in the radiographs, to determine the pathology of the pituitary body. In twenty-three out of twenty-four nonselected cases of Mongolian idiocy, including six of my own, the radiograph