A patient received 2.5 mg vitamin D2 daily for 10 years and presented with increasing skeletal pain and hypercalcaemia. The limbs were painful to touch especially at the insertions of ligaments and tendons, and radiographs showed osteosclerosis with calcification in the periosteum, blood vessels, tendoachilles and plantar fascia. Bone histomorphometry showed increased amounts of osteoid and defective mineralisation despite hypercalcaemia, hyperphosphataemia and raised serum concentrations of vitamin D metabolites. A negative external calcium balance was documented in the presence of enhanced intestinal calcium absorption and an increase in urinary hydroxyproline excretion. Cortisone improved calcium balance and corrected the hypercalcaemia by reducing serum 1,25-dihydroxyvitamin D levels and urinary hydroxyproline excretion.