A total of 24 patients with metastatic renal cell carcinoma were treated with a low-dose cyclic regimen of interferon-gamma (IFN-gamma). The dosage was 50 micrograms IFN-gamma s.c. per day for 5 days every 4 weeks. In 16 of the 24 patients nephrectomy had preceded this treatment. Another immunotherapy had already been performed in 13 of the 24 cases. No complete remission was achieved in any of the patients, all of whom were evaluable. One patient with pulmonary metastases achieved partial response. Stable disease lasting 2 to 12+ months was seen in 5 cases. Tumour progression was observed in 18 patients. Only slight side-effects were noted. Patient selection could be one reason for the wide range of response rates reported for IFN-gamma treatment in the literature.