In this communication, we report for the first time, that immunization of cancer patients with autologous soluble tumor-associated antigens (sTAA) isolated from their own serum prevents the toxic side effects of chemotherapy, improves the patients' clinical status, and has therapeutic effects without chemotherapy. In 2001 and 2002, two cancer patients were treated, during chemotherapy, with autologous sTAA. Another benign tumor-bearing patient was treated with a medicinal herb and autologous sTAA. Doses for subcutaneous injections varied between 2.5 and 3 mg of sTAA in 0.5 ml of sterile distilled water. Injections were performed twice a week or at weekly intervals. In each case, the clinical status of the patient became more stable and healthier. Toxic side effects caused by chemotherapy decreased or even disappeared. No additional toxic side effects were observed after vaccination with sTAA. In the studied cases, a polyp disappeared and a metastatic brain tumor began to encapsulate. No metastases were seen in the case with colon adenocarcinoma. We concluded that vaccination of patients with autologous sTAA prevents the toxic side effects of chemotherapy in cancer patients and improves their clinical status. In the case with the benign tumor, this vaccination activated the host's immune system, prevented progress of the disease and even promoted tumor disappearance. We suggest that immunotherapy with autologous sTAA provides significant clinical benefits in cancer patients and appears to be an important new adjuvant treatment of cancer.