Purpose: To assess the level of occlusion and arterial distribution of calibrated bioresorbable microspheres (BRMS-I and BRMS-II) compared with tris-acryl gelatin microspheres (TGMS) after renal embolization. Materials and Methods: Six rabbits underwent renal embolization with 100-300 μm BRMS-I and TGMS; three rabbits received partial occlusion (group 1, n = 3), and three rabbits received total occlusion (group 2, n = 3). Four other rabbits received 100-300 μm BRMS-II (with higher cross-linking density than BRMS-I) in the left kidneys reaching total occlusion (group 3, n = 4). Coronal sections of the kidneys were histologically analyzed. Ease of injection, microsphere deformation, vessel sizes, and arterial distribution were assessed. Results: The injection of BRMS-I, BRMS-II, and TGMS through microcatheters went smoothly without any clogging. In group 1, BRMS identification was easier than TGMS. In group 2, both BRMS-I and TGMS were observed in all three arterial levels (interlobar, arcuate, and interlobular arteries) without a significant difference (P =.84). BRMS-I were not significantly different from TGMS in the mean diameter of vessels occluded (197 μm ± 23 vs 158 μm ± 21, P =.25) or the microsphere deformation (8.85% ± 0.53% vs 11.80% ± 0.64%, P =.071). In group 3, the arterial distribution of BRMS-II was significantly different from BRMS-I and TGMS (P <.0001). Conclusions: In occluding arteries, 100-300 μm BRMS-I were not significantly different from 100-300 μm TGMS. Arterial distribution of BRMS can be influenced by their cross-linking density.