In order to elucidate the blood serum calcium, inorganic phosphorus, parathyroid hormone (PTH) and calcitonin (CT) content in the course of the development of chronic renal failure (CRF), 80 patients with chronile glomerulonephritis were examined. Of these, in 24 glomerular filtration (GF) was normal, whereas 56 had CRF of varying degree. Thirty-three out of the 80 patients had the nephrotic syndrome (NS). The parameters enumerated were also determined in 45 patients with CRF treated by hemodialysis. In patients without the NS, hypocalcemia was discovered only at the final predialysis stage of CRF, while in the presence of the NS, it was detectable in normal GF and was aggravated as CRF progressed. The PTH level ascended if GF was lower than 40 ml/min, not correlating with calcium concentration in the serum. A direct correlation was disclosed between the PTH level and that of inorganic phosphorus. The role of the latter in stimulation of PTH and CT secretion in CRF is discussed. In patients treated by hemodialysis, the PTH level significantly rose with treatment time increase. There was also a tendency toward elevation of CT concentration. The activity of the osseous fraction of blood serum alkaline phosphatase in patients treated by hemodialysis was increased in 61-84% of cases depending on the treatment period.