Recent publications report increased cardiovascular morbidity and mortality after transurethral prostatic resection (TURP). Repeated breath-ethanol monitoring with a new infrared device permits a highly sensitive peroperative registration of fluid absorption. A prospective study in 52 patients revealed surprisingly high rates of intravascular fluid loads without clinical manifestations. Only 4 patients developed clinical signs of the TUR syndrome. Immunological work-up in 41 patients demonstrated circulating endotoxins and significant rise of endogenous tumour necrosis factor (TNF) in 3 of these patients. In 11 patients transient endotoxins could be detected during resection under prophylactic parenteral antibiosis. In the face of less invasive approaches to benign prostatic hyperplasia, close intraoperative monitoring and antibiotic coverage should be demanded as a routine procedure during TURP. Elective surgery should be delayed until appropriate antibiotic therapy has been given.