In the period 1981-1993, 102 patients underwent surgery for primary hyperparathyroidism (HP). Parathyroid adenoma was found in 81, carcinoma in 4 and hyperplasia in 17 patients. HP was usually diagnosed late with marked skeletal or renal damage, psychiatric symptoms and hypertension. Following the first operation in our institution hypercalcemia was successfully reduced in 100 of 102 patients, in two hypercalcemia persisted after the operation and both were reoperated. Postoperative hypocalcemic syndrome (transitory hypoparathyroidism) due to advanced stage of HP and enormous calcium deficit in bones, occurred in 47% of patients (most frequently with skeletal and hypercalcemic form of the disease).