The aim of this study was to determine the predictors of post renal transplant hypophosphatemia in living donor transplantation Intact PTH(iPTH), biointact FGF23, albumin corrected calcium, and inorganic phosphorus (iP) were analyzed in 63 ESRD (Male 58, mean age 35.65±11.79 years) patients who underwent living donor renal transplantation (Tx) before and at month 1(M1) after transplantation. The native kidney diseases of these patients were chronic glomerulonephritis (n=36), interstitial nephropathy (n=20), diabetic nephropathy (n=6) and polycystic kidney disease (n=1). The upper normal cutoff value of iPTH was considered as >65 pg/ml, and iFGF23 >50 pg/mL, hypo and hyperphosphatemia was defined with iP<2.5 and >5.5mg/dl respectively, hypo and hypercalcemia with corrected for serum albumin <8.5 and >10.8 mg/dL, respectively The mean iP level was decreased by 54.51% at M1 from pre Tx values; however; hypophosphatemia was observed only in 17(27%) patients at M1. Mean FGF23 level was decline by 93.81% at M1 and 23(36.5%) recipients had their FGF23 value above the normal range. Mean iPTH levels was also decreaesd by 67.9% and hyperparathyroidism was observed in 40(63.5%) patients at M1. Hypophosphatemic patients had higher FGF23 (p<0.001) and iPTH (p=0.272) compared to normophosphatemic. At onset of hypophophatemia after Tx; on univarriate linear regression serum iP was significantly correlated with FGF23; uric acid and eGFR; however on multivarriate linear regression using a backward stepwise model; serum iP was significantly associated only with FGF23 levels (p<0.001); but not with iPTH and other factors regulating phosphate metabolism at M1 This study indicate that FGF23 is strongly associated with hypophosphatemia; independently of iPTH early after Tx