SummaryA case showing clinical and radiological evidence of osteomalacia associated with pyelonephritis is reported. Right nephrectomy was performed because there was pyonephrosis on this side.Surgical procedure was followed by complete cure of the osteopathy. Metabolic data (table VII) indicate hypophosphatemia, hypomagnesiemia and excessive urinary loss of P, Mg and Ca before operation.Although a slight systemic acidosis was present, no abnormality of renal acid producing mechanisms was elicited.After operation renal handling of P, Ca and Mg was shown to be essentially normal.These facts demonstrate that, in this case, the renal tubular defect responsible for metabolic disturbances was limited to the right kidney.