Because of difficulties in evaluating bone mineral mass with conventional methods in patients with final renal insufficiency before and after parathyroidectomy, bone densitometry has been tried. During a three year period ten patients have been selected for surgery. The parathyroidectomy performed was total in nine patients and subtotal in one. Bone mineral mass was significantly lower preoperatively in the operated patients than in other patients on regular hemodialysis and also lower than in a normal material. In four of ten patients there was a transient decrease in bone mineral mass after parathyroidectomy. Thereafter there was a significant increase in five of ten patients and in the whole group of patients. Thus bone densitometry was found to be of value in following patients with renal insufficiency selected for parathyroidectomy.