Eighty-one patients were submitted to gynaecological malignancy surgery in a randomized study aimed at the evaluation of the efficacy of defibrotide (40 patients) and calcium heparin (41 patients) in perioperative prophylaxis. They were randomly allocated to defibrotide group (400 mg bid im starting one day before surgery and continuing until the 7th postoperative day) or calcium heparin group (5000 IU bid sc starting two hours before surgery and continuing likewise for 7 days). No cases of DVT diagnosed by means of a Doppler CW were observed in either treatment group. Laboratory parameters have shown similar modifications in the two treatment groups. Three cases of bleeding were observed in the calcium heparin group while no cases of bleeding were detected in the defibrotide group. The results obtained suggest that defibrotide is at least as effective as calcium heparin in perioperative DVT prevention and that the former drug has a possibly better tolerability profile, due to a decisively lower tendency to bleeding.