Alginate gel beads (AGB) were studied as a new material for chemoembolization therapy. AGB were quickly produced by dripping a sodium alginate solution through a cannula into a calcium chloride solution, with bead size controlled by cannular size. AGB containing adriamycin or contrast medium were produced from the corresponding mixture. Sixty percent of adriamycin was eluted from AGB within one hour and 90% within 24 hours, while 95% of iopamidol was eluted in 30 minutes. AGB released these contents slower than gelatin sponge particles. Four dogs underwent transcatheter hepatic arterial embolization with AGB. Normal daily activity was recorded until sacrifice on the fourteenth day. There was no hepatic infarction in those embolized with AGB of 0.5 to 1.0 mm in diameter. Partial liver infarction was found in one with compelled embolization and in two with fragile beads. These observations suggested that AGB constitute an instantly preparable embolic material with slow-release activity and flexible solidity.