Fibroblast growth factor-23 (FGF-23) is a phosphatonine of important value in maintenance of mineral homeostasis. In the 1st part of this review dealing with FGF-23 its composition, mode of action, and regulatory mechanisms of its secretion were described. In the 2nd part of this work, regulatory activity in the calcium-phosphate homeostasis in different stages of chronic kidney disease (CKD) with special attention to increased synthesis of FGF-23 in the course of declined glomerular filtration rate were elucidated. The FGF-23 concentration in dialyzed patients, subjects after parathyroidectomy and patients after kidney transplantation were characterized. The relationship between FGF-23 serum concentaration and cardiovascular morbidity and mortality will be presented in the 3rd part of this review.