We know that irrigating fluid used during transurethral resection of prostate (TURP) is rapidly absorbed through open prostatic venous channels in large amount. The TURP syndrome is symptom complex of hypervolemia & hyponatremia (below 130 mEq/1) due to absorption of irrigating fluid. We studied the change of serum sodium, potassium and symptom of hypervolemia during the perioperative period, in 35 patients undergoning TURP. The aim of this clinical study was to examine the possible relation between the irrigating fluid absorption & the development of hyponatremia after TURP. The results were as follow. 1) Though p value was not acceptable, there waa numerical correlation between the weight of resected prostate and the amount of irrigating fluid. 2) TURP syndrome and severe sodium change were not reported in our studiea, 3) We through the cause of above results that operation time & minimal use of irrigating fluid & minimal bleeding due to advanced operative technique, adequate fluid therapy, and intenaive monitoring of vital sign & physiologic change of patients.