The starting point for the investigation of calcium phosphate ceramics is given by the bone regeneration, including osteoconduction, osteostimulation and osteoinduction. The amount of the autogeneic bone, which can be used for transplantation to induce the organo typical regeneration, is a small one. Calcium phosphate ceramics are used as bone substitute. The basic knowledge of clinical employment is summarized. A new model for investigation of bone regeneration is introduced. In part II the results will be discussed.