Hypercalcaemia developed in 21 patients due to vitamin-D poisoning; 2 were poisoned twice and 2 were poisoned three times. All patients had taken milligram doses of vitamin D, which for 5 patients was inappropriate. For the other 16 patients (mainly with hypoparathyroidism) milligram doses of vitamin D were appropriate; the patients were poisoned either early in therapy, trying to correct the plasma-calcium too quickly, or, later, because of failure to follow up patients properly. 2 patients died as a result of their intoxication. Constant vigilance is essential when patients are taking large doses of vitamin D.