Arteriovenous fistulas commonly occur in cases of renal cell carcinoma, but they rarely produce sufficient left-to-right shunting to cause decompensation of the cardiovascular system. A case of refractory hypertension and congestive heart failure secondary to arteriovenous shunting in bilateral renal cell carcinoma is presented. Renal blood flow studies at the time of staged nephrectomy, together with measurements of cardiac output, established parenchymal arteriovenous shunting as the cause of the patient's cardiovascular symptoms. Subsequent nephrectomy achieved a marked clinical and symptomatic improvement. The causes, diagnosis, and treatment of arteriovenous fistulas are discussed. Although nephrectomy offers dramatic resolution of clinical symptoms, long-term survival depends on the behavior of the neoplasm.