To remove multiple calyceal stones percutaneously is not a simple task. During the act of dilating the pierced channel the stones are apt to drift away towards other parts of the renal cavitary system. For avoidance we recommended the use of Pyeloform, a bicomponent synthetic compound in which chemical reaction between the two substances produces a gel-like matter. This permits the stones partly to be embedded, partly to be fixed against the risk of displacement. described is the effect of Pyeloform in the removal of multiple calyceal stones.