The aim of this study was the analysis and comparison of bone density data obtained by dual-energy X-ray absorptiometry (DEXA) and quantitative ultrasound (QUS) and the follow up of bone density after parathyroidectomy of our patients with primary hyperparathyroidism. The authors performed bone mineral density (BMD) measurements using DEXA (Hologic QDR 4500 C) and QUS (Lunar Achilles Plus) devices in 22 patients with primary hyperparathyroidism between 1997 and 1999 (19 sporadic, 1 MEN 1., 2 MEN II.). Fifteen patients underwent parathyroidectomy (13 adenoma, 2 carcinoma). According to DEXA measurements all patients had osteoporosis. The lowest bone mineral density was detected at the wrist: the mean t-score was -4.00 +/- 1.79. After parathyroidectomy nine patients were followed for a mean of 12.8 months. After one year following surgery the most significant increase in BMD was 14.6%. The QUS values did not correlate with the DEXA data before the operation and no significant changes in stiffness were detected after surgery. The QUS values do not reflect the severity of the BMD decrease by DEXA in patients with primary hyperparathyroidism.