1. A case is described for which the name metaphyscal chondrodysplasia of Jansen is suggested.
2. Biochemical changes were found simulating those caused by hyperparathyroidism, but different and distinctive roentgenographic findings were also evident. Parathyroid exploration was negative for hyperplasia or adenoma.
3. It is postulated that the metabolic changes—hypercalcaemia and hypophosphataemia—may have been secondary to the unverlying bone defect.