disclosed are compositions suitable for use in embolizing blood vessels which compositions comprise a polymer , a biocompatible solvent and a contrast agent . the polymer is selected from the group consisting of polyacrylonitrile , polyurethane , polyvinylacetate , cellulose acetate butyrate , nitrocellulose and copolymers of urethane / carbonate and copolymers of styrene / maleic acid .