Subtotal parathyroidectomy was performed on 34 patients with severe renal insufficiency. The indications were grave clinical symptoms (pruritus, bone pains and mental disturbances), gastric ulcer and radiological abnormalities (metastatic calcifications, osteoporosis, fractures and subperiostal resorption). The serum calcium level was elevated in eight cases. The serum parathormone value was determined in 13 cases, it was elevated in all cases. Less than 500 mg tissue was removed in 12, between 500 and 6000 mg in 19 and over 6000 mg in 3 cases. Nodular hyperplasia was demonstrated in 11 and diffuse hyperplasia in 23 patients. The serum calcium and parathormone levels fell markedly after the operation, and pruritus, bone pains and mental disturbances were markedly alleviated. Complete recovery was achieved only by a successful renal transplantation, but the operation had often a favourable effect on the grave symptoms.