Patients with metastatic solid tumors resistant to conventional modalities will be eligible to participate in a treatment program based on the administration of non-myeloablative immunotherapy (i.e. fludarabine, Cytoxan) followed by interferon injections; subsequently the patients will be treated with mismatched alloreactive donor lymphocytes activated in vitro and in vivo with rIL-2. The aim of this study is based on the recognition of foreign tumor cell surface alloantigens.