This study was a prospective randomized trial to compare adjuvant immunotherapy with Keyhole Limpet Hemocyanin (KLH) after radical nephrectomy. From January 1983 to December 1988, 50 patients underwent radical nephrectomy for category PT 2 N+ and PT 3-4, No-N+, Mo renal cell carcinoma. Postoperatively 25 patients were given adjuvant treatment with the biological response modifier, Keyhole Limpet Hemocyanin (KLH), and 25 patients were in the control group. In each group 2 patients were lost to follow-up. The mean follow-up time was 55 months. Adjuvant treatment with KLH did not appear to improve the prognosis in renal cell carcinoma patients. The 5-year survival rate was 60% in the KLH group and 56.5% in the control group. Progress was seen in 9/23 in the KLH group, 10/23 in the controls. The median survival in patients showing progress was 27 and 28 months in the two groups, respectively. Studies with a combination of low dose cyclophosphamide and KLH revealed a positive immunostimulating effect, which may provide the rationale for further research concerning different KLH doses, schedules or therapeutic combinations.