Surgery is the usual treatment for primary hyperparathyroidism. However, some patients with high surgical risks are not suitable for surgery. For such patients, we propose, as an alternative treatment, ultrasonically guided percutaneous ethanol injection into parathyroid adenomas, in order to induce necrosis of the tumor. We report, here, the results of ultrasonically guided percutaneous ethanol injection into parathyroid adenomas, during a prolonged follow-up period up to 49 months, in a group of 13 patients (median age 79 years) with primary hyperparathyroidism and contraindications for surgery. In seven patients, complete normalization of plasma calcium, phosphorus and parathyroid hormone (PTH) levels was achieved after ethanol injections, with no recurrence of hypercalcemia during a median follow-up period of 28 months (total success). In these seven patients, plasma calcium, phosphorus and PTH levels were normalized 48 h after the successful ethanol injection. In four patients, a partial success was obtained with clinical improvement and normalization of plasma calcium levels but without complete normalization of plasma PTH levels. This partial success is due to incomplete necrosis of the adenoma, as has been confirmed in one patient by histopathological examination. The ethanol injection treatment failed in only two patients. This treatment was always well tolerated and no major side-effects were observed. In conclusion, our results give evidence that ultrasonically guided percutaneous ethanol injection into parathyroid adenomas can be a very useful alternative therapy in patients not suitable for surgery.