Periarticular tumoral calcification is a unique form of soft tissue calcification that occurs infrequently in patients with end-stage renal disease. The mechanism underlying such massive periarticular calcifications is unknown. The radiographic similarity between uremic tumoral calcifications and those found in hereditary tumoral calcinosis, a disorder of calcitriol and phosphorus homeostasis, caused us to examine whether abnormalities in vitamin D metabolism were associated with uremic calcinosis as well. We examined two uremic subjects with massive periarticular tumoral calcifications and found that they had inappropriately high serum calcitriol levels for the degree of renal function, hyperparathyroidism, and hyperphosphatemia. The source of calcitriol could not be identified in one subject, but likely was derived from granulomatous tissue in the other. In the subject with marrow granulomas, we found that calcitonin administration further stimulated calcitriol production. Although epidemiological studies are needed to confirm this preliminary association between calcitriol and uremic tumoral calcinosis, our observations suggest that normal serum calcitriol levels in association with hyperphosphatemia may be a contributing factor in the development of this rare disorder.