Abstract Calcium and Magnesium homeostasis can be disturbed in many ways in the course of chronic renal failure (CRF) . Almost all calcium body content resides in the extracellular space , while the Magnesium almost intracellular space . The concentration of both ions is maintenance is possible via cooperation between many regulating systems in the cell membranes . The aim of our study was to estimate the activity of Ca2+–Mg2+ - ATPase (CMA) , creatinine, urea, sodium, potassium , magnesium , total calcium, inorganic phosphate , Parathyroid hormone, Vitamin D. , and total protein in blood of patients with CRF and evaluate the correlation of Ca2+–Mg2+ - ATPase with Vitamin D , Parathyroid hormone , Ca+2 and Mg+2 . Methods A total of 60 diagnosed CRF patients (30 males and 30 females) their ages ranged from 22-65 years its called G1 while G2 consisted of 60 healthy subjects , The chemicals and kits that were used in this study were of the highest purity. Results in patients groups Ca2+–Mg2+ - ATPase , magnesium , total calcium and Vit. D was Significant decrease in G1 compare with G2 while creatinine, urea, potassium , inorganic phosphate and Parathyroid hormone Significant increases