In metastatic renal cell carcinoma, most conventional antineoplastic drugs have yielded no or little efficacy. To evaluate the tolerance and therapeutic efficacy of second line chemo/immunotherapies, we treated patients with advanced metastatic renal cell carcinoma upon progression after previous antineoplastic therapy employing an outpatient combination of subcutaneous (SC) recombinant interferon-alpha (rIFN-alpha) and intravenous (IV) 5-fluorouracil(5-FU). Thirty-three patients with metastatic renal cell carcinoma received SC doses thrice weekly of rIFN-alpha at 10 million U/m2 over 8 consecutive weeks. Additionally, patients received IV 5-FU at 750 mg/m2 in weeks 1-3 and 5-7; treatment cycles were repeated until disease progression. Of 33 patients, one achieved a complete remission (response duration, 24 months) and two patients presented with partial remissions (median response duration, 7 months) of pulmonary metastases upon rIFN-alpha/5-FU after failing SC recombinant interleukin-2 (rIL-2) and rIFN-alpha. The present chemo/immunotherapy regimen was overall well tolerated with low to moderate systemic toxicity and predominantly constitutional symptoms i.e., fever, chills, and malaise. In summary, the second line outpatient chemo/immunotherapy regimen of SC rIFN-alpha/IV 5-FU demonstrated a limited albeit significant efficacy in pretreated patients with progressive metastatic renal cell cancer.