Parathyroid adenomas are exceedingly rare in childhood. Primary hyperplasia of the parathyroid gland has been reported in infants and young children, but the parathyroid adenoma seems to be almost exclusively a disease of the older age group. Of 140 cases in a recent Mayo Clinic series, the youngest was 14 years old.1The case to be presented, at 7 years of age, represents the youngest child with a functioning adenoma, surgically removed and proved pathologically. It is the purpose of this report to review primary hyperparathyroidism as it is seen in children and to stress two unusual features of this case, namely, permanent neurological damage and an unusual serum magnesium deficit. REPORT OF A CASE A 6-year-old Negro boy was first admitted to the Cincinnati General Hospital on Nov. 11, 1953, with the following history. Five days prior to admission he was listless and complained of headache and aching