Introduction and objectives Urokinase is synthesized by various cells such as kidney, pneumocytes, and phagocytes. It cleaves plasminogen to plasmin and hence stimulates fibrinolysis. Urokinase breaks down the matrix protein within the stone and thus prevents stone formation and growth. Urokinase concentrations are lower and urokinase gene 3'-UTR T/C polymorphism is higher in patients with recurrent stones. Our aim was to investigate the role of urokinase gene 3'-UTR T/C polymorphism in childhood recurrent stone disease.