A comparative study of direct radiological magnification technique was made of 22 patients with primary hyperparathyroidism, 15 patients with secondary hyperparathyroidism, and 17 patients without changes in bone structure. Only regarding the summation of all radiologically visible changes in bone structure, a hyperparathyroidism can be suspected. The differential diagnosis of primary and secondary hyperparathyroidism is mostly impossible. Furthermore we were able to demonstrate that early discrete changes in bone structure are more easily diagnosed in magnification technique than in standard technique. Therefore we regard the direct radiological magnification technique as an adequate method for patients, in whom hyperparathyroidism is suspected.