In vitro measurements have proved that the polymerization time of n-butylcyanoacrylate (Histoacryl) can be delayed markedly and controlled by adding an oily radiopaque material. Our animal experiments have shown that a mixture of Histoacryl and Lipiodol ultrafluid at a 1:3 ratio provided an optimal embolization material with good flow properties, polymerization time of approximately 7 sec and excellent contrast definition. This mixture may be handled easily, with a minimum of risk involved when used with a 40% glucose solution.