OBJECTIVE To develop and evaluate a bioresorbable spherical material for embolization. METHODS New bioresorbable hydrogel microspheres were prepared from carboxymethyl cellulose and chitosan by using an inverse emulsion method. Size distribution of the microspheres was determined with a microscope, and the colorability was tested with Evans blue dye. The compressibility was examined with a texture analyzer. After sieving, the suspendability of the microspheres was tested in saline solution/contrast agent mixture in different ratios, and then the injectability was tested with microcatheters (lumen sizes of 0.0165, 0.019, and 0.027 inches). The in vitro degradability tests were performed in a lysozyme solution. Cell culture study of the microspheres was performed with human fibroblasts. RESULTS The microspheres exhibit diameters of 100-1,550 μm with a transparent appearance. Their fracture force can reach 0.58-0.88 N, and fracture deformation varies from approximately 70% to 95% of their original size. These microspheres can be colored by Evans blue dye, and uniform subgroups of microspheres can be readily obtained by sieving. Within 3 minutes, the microspheres form a stable suspension in a 4:6 contrast agent/saline solution mixture, which can be easily injected through microcatheters without aggregating or clogging. These microspheres are biodegradable, with degradation times varying from 2 weeks to 1 month, depending on their composition. Cell culture studies reveal no adverse effect on the growth of human fibroblasts in the presence of the microspheres. CONCLUSIONS A biodegradable and noncytotoxic microsphere was successfully prepared. It can be well suspended in the contrast solution and easily injected through a microcatheter.