Hypertrophic pulmonary osteo-arthropathy, as the syndrome is commonly designated in this country, has recently been observed under circumstances different from any heretofore described. A patient whose history I shall give in some detail returned to the clinic following an operation of subtotal thyroidectomy, presenting most exaggerated clubbed fingers and swelling of the lower part of the legs. Roentgenographic studies of the bones revealed a remarkable picture of subperiosteal new bone formation, involving most of the long bones of the skeleton, but showing a change in the bones of the hands which had not been seen by the clinicians or the roentgenologists at the Johns Hopkins Hospital. Since finding in an article by Holthusen1 the print of an x-ray picture of a hand showing similar changes, I have come across quite a number of articles, particularly in the German literature, which discuss this condition at great length. The cause of