The data of 24 patients, operated for different types of hyperparathyroidism were reviewed in order to evaluate the evolution of calcium levels during the first week following surgery. A correlation with the preoperative values of alkaline phosphatase could be demonstrated. It may be concluded that in the primary affected patients a stay in the ICU, only for hypocalcemia-related problems, is not required. In secondary hyperparathyroidism however, the more spectacular drops of calcium levels and the risk of other vital complications, justify a follow-up in the ICU for at least 48 hours.