The phenotype of peripheral blood lymphocytes of 27 renal cell carcinoma patients before and at the end of subcutaneously given rIL-2 therapy was determined by two colour flow cytometry. Therapy induced changes in peripheral blood leucocyte composition and phenotypes were comparable to those reported for intravenously given rIL-2. The present paper shows a correlation between the 'activation status' of the patient before therapy and eventual response.