Prostate's surgery is an haemorrhagic one owing to difficulties of surgical haemostasis and anomalies of the blood coagulation. The aim of this study to assess haemostasis anomalies after protatectomy for benign prostatic hyperplasia (BPH). We have performed a prospective study including 50 men of more of 55 years old. All of them underwent suprapubic open prostatectomy. Significant pertubation of haemostasis, particularly fibrinolysis has been found. We have noticed fibrin degradation product in 88% of cases after intervention versus 62% before (p < 0.001) and a decrease of plasminogen rate in 94.4% of operated patients versus 82% before. The older the patient were, more important were the pertubations. Moreover, the anomalies were most important when the duration of surgery lasted more than one hour and when the BPH was voluminous. However, the disturbance of haemostasis was rarely associated to clinical symptoms. So, we do not recommend any therapeutic when clinical symptoms are absent. Biological screening the day of surgery, the day after and one week later are necessary to prevent haemorrhage.