From 1960 to 1988, we successfully treated 1,200 primary hyperparathyroid patients. The serum calcium level was higher than 3.75 mmol/l (150 mg/l) in 75 patients. Sixty-five patients had acute primary hyperparathyroidism and 10 had asymptomatic severe hypercalcemia. Before admission to our department, most of the patients were given medication to lower their serum calcium levels. Analysis of our diagnostic and therapeutic experience leads us to insist upon the importance of prompt medical treatment and rapid surgical intervention. Only surgery can adequately treat severe hyperparathyroidism.