The effect of peri-operative blood transfusion on survival after surgery for renal carcinoma was studied in 201 patients. In addition to blood transfusion, several other factors were included in a multivariate analysis. Using Cox's proportional hazards model, transfusion of more than 4 units of blood was found to be an independent prognostic factor in addition to tumour stage, erythrocyte sedimentation rate and macrohaematuria.