The multitude of classic manifestations of paraneoplastic thromboembolism (TE), including new aspects, are reviewed. This emphasizes the complexity of the situation that the physician faces in dealing with paraneoplastic TE. Unexplained TE may serve as a hint for the presence of a hidden tumor. However, efforts to uncover such an underlying malignancy often are unrewarding. The view has been expressed that it is inappropriate to conduct an extensive search for an occult neoplasm unless there are more specific indications. A recent study defined clues that might separate patients with TE and occult cancer from those unaffected by a malignant neoplasm. The study of the hemostatic alterations in patients with cancer underscores the triple role of cancer cells in the pathogenesis of TE: injury to the endothelial lining of blood vessels, activation of platelets, and activation of blood coagulation and depression of anticoagulant functions. The failure of standard anticoagulant treatment in many instances is better understood. Novel approaches to treatment include low-molecular-weight heparin(s) for long-term administration or, alternatively, the initial placement of a Greenfield filter in the vena cava instead of anticoagulant therapy. Either of these may provide superior results in comparison to standard heparin treatment.