A girl, aged 16 months, with idiopathic hypercalcemia (failure to thrive, characteristic face, supravalvular aortic stenosis) was observed. Her serum calcium level was between 14 and 20 mg/l00 ml. Both her father and brother were mentally retarded and had calcium deposits in their corneae. Their serum calcium values were 11.9 and 13.0 mg/100 ml, respectively, with increased urinary output of calcium. The family history is suggestive of autosomal dominant inheritance of the disease.