An embolization device includes a plurality of highly-expansible embolizing elements disposed at spaced intervals along a filamentous carrier. In a preferred embodiment, the carrier is a suitable length of very thin, highly flexible filament of nickel/titanium alloy. The embolizing elements are separated from each other on the carrier by radiopaque spacers in the form of highly flexible microcoils made of platinum or platinum/tungsten alloy. In a preferred embodiment, the embolizing elements are made of a hydrophilic, macroporous, polymeric, hydrogen foam material. The device is particularly suited for embolizing a vascular site such as an aneurysm. The embolization bodies have an initial configuration in the form of small, substantially cylindrical "micropellets" of small enough outside diameter to fit within a microcatheter. The bodies are hydrophilically expansible into an expanded configuration in which they substantially conform to and fill the vascular site while connected to the carrier.
