We describe a girl with congenital hyperparathyroidism who presented soon after birth with respiratory distress, hypotonia, feeding difficulties, and bone deformities. Hypercalcaemia, hypophosphataemia, and raised alkaline phosphatase were present and plasma parathyroid hormone levels measured by radioassay and bioassay were raised. X-rays showed gross demineralisation with metaphyseal fractures, erosions, and sub-periostal reaction along the bones. Following surgical removal of four hyperplastic parathyroid glands and subsequent maintainance therapy with 1-alpha-hydroxycholecalciferol there has been virtually complete reversal of her bone abnormalities.