Neonatal hyperparathyroidism secondary to maternal hypocalcemia in pregnancy is a rare disorder.1 The effects of secondary hyperparathyroidism in patients with renal failure, including renal osteodystrophy, are well described.2 Neonatal hyperparathyroidism in the presence of maternal renal disease and secondary hyperparathyroidism has not previously been reported. We here present a unique situation in which a neonate developed congenital hyperparathyroidism secondary to maternal hypocalcemia as a consequence of renal tubular acidosis. This report emphasizes the significance of maternal serum calcium concentrations in pregnancy in determining the parathyroid state of the fetus and neonate. METHODS For this report, the following biochemical methods were employed and normal ranges, as measured in our laboratory, are indicated in the tables.