The review of 340 own cases of hyperparathyroidism surgery shows, that only the concentrations of calcium and parathormone in serum are of interest for the diagnosis. Further biochemical analyses and function tests are not specific enough to serve as indicators for hyperparathyroidism and serve only as secondary reinforcements of the diagnosis. There are many methods for the preoperative localisation but only the computer tomography with simultaneously given contrast medium or a refined sonography seem to be reproducible. 94% of the cases are cured by surgery. The further development of urolithiasis is certainly reduced after the successful operation, however, in about one third of the cases with normocalcemia, a recurrent and marked increase in size of the stones present was observed postoperatively. The possibility of such a continuous growth gives reason to observe closely the development of urolithiasis in order to be able to react promptly by means of lithotomy.