A neonate girl experienced generalized seizures on the 19th day after birth. Examination of the girl's serum showed hypocalcemia, hypomagnesemia, and hyperphosphatemia, compatible with the diagnosis of hypoparathyroidism. The seizures were controlled following administration of calcium, magnesium, and oral aluminum hydroxide. A study of urinary phosphate excretion in the child suggested that it took her approximately three months to return to euparathyroid state. As a result of the child's illness, the mother was examined, and was found to have hyperparathyroidism. The mother was cured following resection of a parathyroid adenoma.