Hydroxyapatite/hyaluronic acid (HAp/HyA) and hydroxyapatite/chondroitin sulfate (HAp/ChS) microparticles, which show the high adsorption ability of proteins, high biocompatibility and osteoconductivity, are potential scaffolds for a time-controlled BMP release. The present study evaluated the biocompatibility and osteoconductivity of the composites after injection into bone defect. Drilled bone holes were made at tibia and femur of Japanese white rabbits, and HAp/HyA or HAp/ChS was implanted into each bone hole using an injection syringe. After 2 and 4 weeks of implantation, rabbits were sacrificed and histological observations were conducted with HE, TRAP, and ALP staining. Histological observations revealed that HAp/ChS has superior biocompatibility compared with HAp/HyA, and 20% HAp/ChS promotes bone formation as well as osteoblast activities compared with lower ratios of HAp/ChS.