This experiment was designed to study the osteogenic potential of adding medical-grade resorbable calcium sulfate mixture to grafting materials for filling osseous defects. Twelve New Zealand rabbits were divided into an active group of 10 animals and a control group of 2 animals. The median condyle of each femur was drilled to create 8-mm-deep cavities. Active osseous defects consisted of 20 cavities and were filled with Osteograf, BOP, or Capset (calcium sulfate) alone; a mixture of Osteograf and Capset; or a mixture of BOP and Capset. Osteograf and BOP were each mixed with Capset in a 4:1 ratio. Each grafting material filled 4 osseous cavities, and 4 osseous cavities were left unfilled to act as controls. The observation period was 8 weeks. Block sections of the femoral heads were prepared for decalcified histologic assessment. It appeared that mixing grafting materials with calcium sulfate powder in a 4:1 ratio, respectively, facilitated the process of osteogenesis and increased new bone bonding to remnants of the grafting materials, in spite of the poor osteoconductive property of BOP and moderate osteoconductivity of Osteograf. However, calcium sulfate material alone is not recommended for use as a bone filler. Keywords: bone substitutes, calcium sulfate, osteogenesis