The existence of immunosuppressive factors which impair the clinical effect of treatment using IL-2 or lymphokine activated killer (LAK) cells has been reported in the serum of patients with renal cell carcinoma. For the purpose of eliminating these immunosuppressive factors, plasmapheresis combined with adoptive immunotherapy using LAK cells was performed in ten patients with stage IV renal cell carcinoma. Immunological examinations revealed that the number of peripheral blood lymphocytes, NK activity and the ratio of Leu 11 positive cells were increased during the treatment. Of the 9 evaluable patients, one has a partial response, 5 showed no change and 3 had progressive disease. In addition to the one partial response, the size of some metastatic lesions in the lungs decreased in 2 patients during the treatment. As serious side effects, brain edema progressed in 2 patients with brain metastases and acute hepatitis due to plasmapheresis was noted in one patient. Moreover, transient and reversible renal dysfunction developed in most patients. These reuslts indicated that plasmapheresis combined with adoptive immunotherapy using LAK cells is a useful therapy for patients with advanced renal cell carcinoma.