Deep venous thrombosis (DVT) can be a significant complication of the postoperative course in gynaecological surgery, because of traumatism and compression to which the vascular pelvic structures are subjected. A protocol was therefore designed to evaluate the effectiveness and tolerability of defibrotide, a new antithrombotic and profibrinolytic drug, compared with low-dose heparin. The study was conducted on 102 women, undergoing major gynaecological surgery for benign and malignant affections, randomly assigned to the following two treatment groups. A) defibrotide (400 mg i.v./i.m. b.i.d., starting the day before the surgery for 8 days); B) calcium heparin (5000 IU s.c. b.i.d., starting on the day of surgery, for/days). Clinical, haematological and instrumental (Doppler ultrasound) parameters were assessed and no major events were noted in either of the two treatment groups though in the calcium heparin group, 2 patients showed clinical signs of DVT (not confirmed by Doppler ultrasound) and no side effects were noticed, except for a cutaneous rash in one defibrotide patient and an episode of bleeding on the third postoperative day in a patient treated with calcium heparin. Defibrotide proved as effective as calcium heparin in the prevention of DVT in gynaecological surgery.