Abstract: This invention provides therapeutic methods for inhibiting tumor metastasis and for treating primary tumors. The methods of this invention do not cause serious side effects and will be effective for a broad spectrum of cancerous diseases. In particular, the invention discloses a novel method comprising administering to a mammal a preparation of intravenous immunoglobulin (IVIG). The IVIG preparation to be administered according to this invention may contain intact immunoglobulin molecules or fragments of immunoglobulins. The preparation is administered parenterally, preferably via intravenous, intracavitary or subcutaneous routes, either as a sole agent or in combination with other agents or methods which are commonly used for cancer treatment.