Enhanced osteobonding abilities of electrical polarized hydroxyapatite (HA) ceramics were statistically evaluated by a bone morphometric technique. HA ceramics with an average charge of 3.9 μCcm⁻² were implanted in tibial and femoral diaphyses of New Zealand white rabbits. Estimation of the affinity index, defined as the ratio of the direct bonding length to the HA ceramic length, significantly showed more active osteobonding ability with a negatively charged surface than with a positively charged surface and a nonpolarized HA 1 week after administration. The enhanced osteobonding ability attributed to the stimulated osteoids in the vicinity of the positively charged surface ranked above the nonpolarized surface. Although amounts of the newly formed bone on the HA surfaces increased with implantation period in all of the observation areas, the negatively charged surface was almost covered with bone and had the best index value of 94.0% at 4 weeks. The superior osteobonding activity of the negatively charged surfaces was statistically proven. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 68A: 90–94, 2004