Hydroxyapatite is a well-known biologic material intended for intraosseous implantation which is widely used in practical dentistry. The agent causes no inflammatory reaction at the site of administration and is not characterized by acute or chronic toxicity. The possibility of development of specific contraindications against hydroxyapatite has not yet been studied; such contraindications might be connected with its possible immunotropism and allergenic activity which are to this or that measure present in all materials used for implantation into the bone. Since hydroxyapatite is known as surfactant, we used in our studies its modification characterized by the highest specific surface known at present, and therefore the most biochemically active. "Cold", that is, not exposed to high-temperature treatment ceramics was used in order to prevent reduction of hydroxyapatite reaction capacity. Complex of animal experiments showed that hydroxyapatite cannot possess immunotropic or allergenic characteristics.