Secondary hyperparathyroidism is a common complication of chronic renal disease, Clinical signs and symptoms tend to be severe and often are not controlled with medical measures, When medical therapy fails, parathyroidectomy becomes necessary, Recurrent hyperparathyroidism is not uncommon following surgery, One cause of surgical failure is parathyromatosis, which has been described as multiple nodules of hyperfunctioning parathyroid tissue scattered throughout the lower neck, superior mediastinum, or the arm if autotransplantation has been performed, Five cases of parathyromatosis in patients with chronic renal failure were identified, Clinical characteristics, course, and prognosis of the patients are reported, All patients had evidence of renal osteodystrophy and complained of severe pruritis and bone and/or joint pain, Three of the five patients had evidence of soft tissue calcification, two complained of muscle weakness, two had multiple fractures, and two eventually died of complications resulting from parathyromatosis, In four of five cases, surgical and medical management were ineffective, The patients described illustrate the severe morbidity and mortality associated with the parathyromatosis in the setting of end-stage renal disease, The pathogenesis remains controversial, Although primary prevention appears to be the most effective means of avoiding this complication, it is mandatory that meticulous care be taken during surgical manipulation, If such measures fail, calcium supplementation, calcitriol, and phosphate restriction may be tried. (C) 1996 by the National Kidney Foundation, Inc.