In 1932 we1reported a case of acute hypercalcemia caused by accidental overdosage with parathyroid extract. Search of the literature reveals no other such report in man. A white boy, aged 5 years, who was being treated for severe essential purpura haemorrhagica, had received hypodermically 5 cc. (100 units) of parathyroid extract daily for a period of five days. The earliest symptom of overdosage that he presented was vomiting. This gradually increased in severity. He became progressively listless until physical depression rendered him actually in a critical condition. He was apathetic and extremely lethargic. He had an irregular fever, which reached a high of 103 F. On the beginning of the sixth day the cause of his condition was recognized and the extract was stopped. During the period of treatment (five days), therefore, he had received in all 25 cc. (500 units). The blood serum calcium was determined to