Systematic study by high resolution real time ultrasonography of the parathyroïd glands unequivocally showed parathyroid hyperplasia in 13% of 60 patients on chronic hemodialysis. Hyperplasia was associated with greater severity of hyperparathyroidism, as demonstrated by subperiostal bone resorption and increased serum levels of alkaline phosphatase, parathormone and calcium. Correlation between ultrasonographic and surgical findings in 5 patients was excellent, and actual weights of removed hyperplastic glands were correlated to calculated volumes. The demonstration of hyperplastic parathyroid glands by ultrasonography was of great help for surgical indication in cases where the classical biochemical and radiological parameters were unavailable or of uncertain significance. In absence of hypercalcemia and/or of hyperphosphoremia which may hinder "medical parathyroidectomy" by vitamin D metabolites, ultrasonographic demonstration of hyperplastic glands represents an unresolved problem as to the choice of surgical or medical parathyroidectomy.