The authors designed a clinical trial to assess the impact of aspirin (ASA) (600 mg four times daily) on the constitutional sequelae of recombinant leukocyte A interferon (IFN-alpha 2A), 20 X 10(6) U/m2 thrice weekly, in 29 patients with advanced renal cell cancer (RCC). Aspirin provided no meaningful amelioration of side effects compared to our prior experience of IFN-alpha 2A alone. Interestingly, the objective response rate of 34% (10/29) was considerably higher than the 15% recently reported from an aggregate of 344 patients participating in 14 prospective clinical trials. In light of small numbers, subtle selection biases, and the well-recognized hazards of retrospective analyses, currently it is unclear if the apparent therapeutic advantage from ASA plus IFN-alpha 2A reflects chance occurrence or therapeutic potentiation from ASA. A randomized trial is planned to determine if ASA may have enhanced the efficacy of IFN-alpha 2A in patients with advanced RCC.