ABSTRACT: The authors discuss about epidemiology, etiopathogenesis, risk factors, prophoilaxis of deep venous thrombosis and pulmonary embolism in patients operated. They report an analisys of their experience, confirming that the incidence of deep venous thrombosis and pulmonary embolism is larger in patients under 60 years old, while over 60, the incidence is similar between neoplastic and non neoplastic subjects.