Recent advances in the knowledge about the mechanism of biological calcification was reviwed with special reference to the regulator proteins for this mechanism. Four important factors involved in this process were pointed out. These are; (1) the cells that form calcified tissues, (2) the organic matrices, (3) calcium and phosphate minerals and (4) the regulators for calcification. Generalized concept of calcification process was described in terms of these four factors. There has been an inconsistency between the facts that physiolosical extracellular fluids are, supersaturated in calcium and phosphate with respect to hydroxyapatite but it also are undersaturated with respect to the formation calcium phosphate de novo. Various theories including the booster, nucleation and inhibitor theories that have been proposed to explain this inconsistency, were criticized. It was emphasized that the systematic function of the regulator proteins for calcification may be a key to resolve the contradiction and to understand this complicated biological phenomenon.
