Thromboembolic complications represent the second leading cause of death for cancer patients. Even though the correlation between cancer and a hypercoagulable state has been widely recognised, the pathogenesis of thromboembolism during malignancy is not yet entirely understood. The direct or indirect activation of the coagulation cascade favours neoplastic dissemination and metastasis. Disordered coagulation is encountered in up to 90% of cancer patients, although only 15% of them develop a localised acute or chronic deep venous thrombosis or a disseminated intravascular coagulation. This risk is significantly increased by chemotherapy, hormone therapy, surgery and central venous catheters. Therefore, much effort is needed to develop efficient prophylaxis and treatment, to reduce recurrence and bleeding and finally, to improve quality of life. Better knowledge about the biochemical bases of the coagulation process represents a pivotal step in cancer biology comprehension and global therapeutic management.