Polyuria is a common finding after renal transplantation, and 24hour urine volume (24huv) up to 15 liters is not uncommon .in this polyuric state variation in pK and pNa may occur. To describe this issue and its clinical significance, we evaluate pK and pNa concentrations in first two weeks after kidney transplantation. Daily pK, pNa, Creatinine (Cr) and 24huv was recorded for 185 consecutive renal transplant recipients. Dialysis was done on the day before transplantation in all patients (pts). Pts with delayed graft function (need to dialysis) were excluded. Among 185 pts 109 (58.9%) were male, mean of age was 38.82 years (range 12-80). Mean of pre transplantation dialysis time was 16.59+-9.84 months (range 0- 48m). Mean of Cr on first and 14th day were 4.84+-2.23 and 2.05+-2.03 respectively. Mean of pK on first and 14th day were 3.99+-0.61 and 4.02+-0.65 respectively. Hypokalemia (pK<3.5) and hyperkalemia (pK>5.5) were seen in 19.22% and 3.95% of pts respectively. Most of hypokalemic episodes (69.54%) occurred on second day and hyperkalemic episodes (59.84%) on 13th day after transplantation. Mean of pNa on first and 14th day were 131.77+-6.19 and 136.59+-4.74 respectively. Hyponatremia (pNa<135) and hypernatremia (pNa>145) were seen in 40.83% and 11.9% of pts respectively. Most of hyponatremic episodes (72.34%) occurred on first day and hypernatremic episodes (68.98%) on 13th day. Mean of 24huv on first and 14th day were 14190.06 +- 6932.55 and 2394.02 +- 994.93 ml. There was not any severe hyponatremia (pNa<125), severe hypernatremia (pNa>155) and severe hyperkalemia (pK>6.5), but severe hypokalemia (pK<3) occurred in 6.2% of pts which mandated K supplementation. We conclude that with good renal function after renal transplantation pK and pNa variations tend to be within normal ranges and only in the first three days severe hypokalemia may occur rarely.