This study analyzes the causes of different fluid absorption and loss of blood in TURP (transurethral resection of the prostate) and also compares TURP with TUVRP (transurethral vaporesection of the prostate). Continuous intraoperative, intravesical pressure measurement and registration of the extent of fluid absorption (measurement of C(2)H(5)OH in the patient's expiratory air) and precise intra- and postoperative analysis of serum and ASTRUP analysis made it possible to differentiate between high- and low-pressure TUR. In addition positive and negative characteristics of TUVRP could be examined. When fluid absorption was registered, a clear correlation between C(2)H(5)OH absorption and decrease in serum concentration of sodium could be seen, making sodium in serum a good marker of fluid absorption. Neither the duration of the operation nor the size of the adenoma had an influence on fluid absorption and loss of blood, but sinus bleeding and capsular lesions, especially in high-pressure TUR, had a significant influence. An advantage of low-pressure TUR, especially in "low compliance bladder," could be clearly seen. No benefit concerning fluid absorption and loss of blood was seen in cases of total resection by TUVRP. In cases of palliative, planned TUR (elderly patients with multiple risk factors) a TUVRP is recommended.