Thirty-four patients with progressive advanced renal cell carcinoma (RCC) were treated with high-dose tamoxifen (HD-TAM) 100 mg/m2 p.o. daily until progression. The overall remission rate was 12%, including 1 complete remission. Seventeen of the thirty-four (50%) patients had minor remission or no change. Taking into consideration the documented progression prior to tamoxifen therapy, further tumour growth could be arrested in 62% (1 CR, 3 PR, 17 MR/NC) of the patients. Median response duration for CR/PR was 20 months (range 6-21+) and median progression-free survival for MR/NC was 6 months (range 2-15). The one-year survival rate was 41%. Patients with only pulmonary metastases, good performance status and prior nephrectomy seemed to have a better survival. Side effects were comparable to those of conventional doses of tamoxifen (20-30 mg p.o. daily). These data suggest that HD-TAM may be a useful therapeutic approach with low toxicity, considering that, in metastatic RCC, the treatment intent is at best palliative.