Aim. To study the role of the morphogenetic proteins FGF-23 and Klotho in the progression of chronic kidney disease (CKD) and in the development of cardiovascular events, inflammation, protein-energy deficiency, and other complications. Subjects and methods. Examinations were made in 70 patients with Stages I-VD CKD: 41 with chronic glomerulonephritis (including 10 with nephritis in the presence of diffuse connective tissue diseases), 22 with tubulointerstitial nephritis, and 7 with hypertensive nephrosclerosis. There were a total of 30 men and 40 women whose age was 20 to 84 years; the mean age at the study inclusion was 41±6.7 years. The serum levels of FGF-23 (Human FGF-23 ELISA kit using monoclonal antibodies to complete molecule of FGF-23) and Klotho (Human alpha-K1 ELISA using anti-Klotho antibodies) were investigated in all the 70 patients with CKD. Results. The sera of all the examinees with CKD showed elevated FGF-23 and decreased Klotho levels, the magnitude of a change in which increased from Stage I to VD. In patients with different stages of CKD, the increase in FGF-23 levels, as glomerular filtration rate reduced, outstripped that in the serum levels of phosphorus and intact parathyroid hormone. There was a strong correlation of the serum level of the morphogenetic proteins, Klotho in particular, with proteinuria, C-reactive protein level, protein-energy deficiency, indicating the pleiotropic effects of these proteins. There was also a strong correlation between serum Klotho and ferritin levels and transferrin saturation percentage, which suggests that Klotho may be involved in iron regulation. Conclusion. The results of the investigation lend credence to the experimental and clinical findings that the serum levels of the morphogenetic proteins FGF-23 (an increase) and Klotho (a decrease) are early markers for progressive CKD and that their changes begin just in Stage III CKD and progress as renal failure worsens.