Four patients had hypophosphatemia: two from adult-onset vitamin D resistant rickets with associated benign mesenchymal tumors; the third patient had intestinal malabsorption, and the fourth used antacids excessively. The illnesses of the first two patients originally were misdiagnosed as ankylosing spondylitis; one of these two had fused sacroiliac joints, the other had lesser radiological changes in these joints. The third patient had peritendinitis calcarea with episodically inflamed joints. The fourth had a myopathy and sensory polyneuropathy. In each instance, there was a lengthy delay before the syndrome's association with hypophosphatemia was recognized. In two patients the symptoms ceased soon after the serum phosphorus levels had been normalized. The rheumatic manifestations of hypophosphatemia can be prominent but may be readily cured.