[en] Although chemoembolization advantageously combines arterial embolization of the vascular supply of a neoplasm with controlled intra-arterial infusion of chemotherapeutic drug(s), its application is limited by the lack of appropriate and reliable embolization materials. Recently, calibrated microspheres of poly(D,L)-lactide have proved to be promising in embolization. Nevertheless, repetitive chemoembolization requires the availability of microspheres degradable within a few days. For this purpose, microspheres consisting of a blend of two polyesters of a very different molecular weight (Mn =65 000 and 3500 in a 16:84 wt. ratio) have been prepared and injected in the renal arteries of rabbits. The in vivo fate of these two component microspheres has been compared by radiology and histology to microspheres prepared from the high molecular weight poly(D,L)-lactide. Furthermore, the in vivo degradation of the polymer has been measured by size exclusion chromatography after quantitative reextraction from the embolized kidney. Degradation kinetics has been compared to data previously reported in vitro. According to the observations performed during the in vivo study, the 50/50 microspheres appear more useful for the chemoembolization of tumors.