It is accepted that the laboratory and clinical so-called "transurethral resection syndrome" reflects passage into the body of a large fraction of the water used to perfuse the field of endoscopic resection. The major complete syndrome (dyspnoea, nausea, hypertension, raised central venous pressure, bradycardia then pulmonary oedema, cerebral oedema, cardiovascular shock and renal insufficiency) is rare: 1.5 per cent of cases of transurethral resection of the prostate in the literature, 0.6% in a series of the last 300 resections performed by the authors (2/300). Also was it not possible to hope for a complete physiological study of sufferers from this complication. Nevertheless, it may be considered that all transurethral resections of the prostate may be associated with similar movements of water to a minimal extent. In order to attempt to demonstrate this, the authors studied in a series of 19 patients pre- and postoperative blood volumes by a radio-immunological technique using pre- and postoperative serum albumin haematocrits. In this short series, patients who had undergone a short endoscopic resection (35 minutes on average) of a small adenoma (13 grams on average) with a mean irrigation of 10 litres of water rendered isotonic by the addition of glycocolle, without any transfusion or infusion being necessary during the course of the resection, the conclusion was simple: no variation in blood volume was demonstrated. Is the physiopathological hypothesis advanced to explain this phenomenon false? And is the problem in fact one of peroperative septicaemia?