Moderate hypercalcaemia occurred in a 17-year-old male who was immobilized with abdominal and right hip sepsis for 9 months after a motor vehicle accident. The hypercalcaemia was due to bone resorption, with a urine hydroxyproline:creatinine ratio of 0.203 (normal less than 0.017) and a urine calcium loss of 22.9 mmol/24 hr, associated with impaired renal function. There was radiological evidence of severe bone demineralization in the pelvis over 42 weeks. Radiocalcium absorption, using 47Ca, was decreased (0.17, normal range 0.35-1.30), renal tubular maximum for calcium reabsorption was decreased (1.61 mmol/1 glomerular filtrate, normal range 1.8-2.2), the serum parathyroid hormone concentration was in the low normal range (3.2, 3.6 u/l, normal range 2-6) and the plasma 1,25-dihydroxy-vitamin D concentration was decreased despite a normal 25-hydroxy-vitamin D concentration, indicating suppression of the parathyroid, 1,25-dihydroxy-vitamin D axis. The patient was found to be hypogonadal at 41 weeks after admission and testosterone therapy was begun, with associated improvement in mobilization and a reduction of the hypercalcaemia.