A 51-year-old woman on peritoneal dialysis for chronic renal failure secondary to diabetic and nonsteroidal anti-inflammatory drug nephropathy was referred for a Tc-99m MDP bone scan to assess firm subcutaneous plaques in the sacral and gluteal regions. This showed extensive superficial tracer localization in the subcutaneous tissues as well as visceral tracer activity in the myocardium, lungs, stomach, and kidneys. These findings were typical for calciphylaxis (calcific uremic arteriolopathy), a form of metastatic calcification encountered in patients with chronic renal failure that is characterized by subcutaneous soft tissue calcification, painful ulcerations, high morbidity, and mortality. Treatment with sodium thiosulfate resulted in dramatic scintigraphic improvement.