Idiopathic hypercalcemia in infants is a disorder of calcium metabolism generally unknown to the radiologist, but being recognized with increasing frequency by our pediatric colleagues as a specific abnormality. The disease usually has an abrupt onset in early infancy, after several months of normal development. It is manifested clinically by loss of weight, anorexia, constipation, vomiting, and hypotonia. Laboratory studies disclose hypercalcemia, elevation of the blood urea, and occasionally evidence of renal acidosis. These features are present in the two recognized forms (1) of the disease, the one transient and the other chronic and severe. In the more common transient type the disease is benign and self-limiting after a course of several months, and there are no distinctive roentgen findings. All reported cases (2–6) of the severe chronic form, on the other hand, have shown signs of physical and mental retardation, hypertension, systolic heart murmur, fretfulness, and radiographic evidence of osteosclerosis. It is the purpose of this paper to bring to the attention of the radiologist the roentgen features of the severe form of idiopathic hypercalcemia. A more detailed account of the clinical and laboratory features of the case has appeared elsewhere (7). Case Report N. H., a 17-month-old white female infant, was admitted to the Texas Children's Hospital on April 5, 1954, because of failure to develop normally. She was born prematurely on Nov. 2, 1952, after a precipitous labor of thirty minutes at about seven and one-half months of an uncomplicated second pregnancy. Her birth weight was 3 pounds 14 ounces. Development had been normal until the age of six months, at which time the weight was 12 pounds 2 ounces. There had then occurred an abrupt cessation of growth. At four months of age the child became irritable, and constipation developed, requiring daily suppositories. From birth to three months of age she was given Alactin, and then an evaporated milk formula. At ten months of age this was changed to Similac 1:1. Solid baby foods, which were begun at three months, were taken readily on occasion but poorly after the age of six months. Supplemental vitamins had been given in normal quantities. Teething began at approximately seven months, and between that age and seventeen months six incisor teeth had made their appearance. At ten months of age the child could roll from side to side but could not sit alone or crawl. At thirteen months a partial paralysis of the left side of the face occurred. Recovery ensued within thirty days but was followed by a gradual weakness of the right side of the face. Physical examination at seventeen months showed the patient to be about the size of a six-month infant, both physically and mentally retarded. She cried fretfully and was unable to sit or crawl. She could not talk but uttered an occasional unintelligible sound.