Bilateral renal arteriovenous (AV) fistulas were discovered in a patient with refractory hypertension. The lesion in the right kidney appeared to be congenital, whereas the etiology of the left-sided lesion could not be determined. Ablation of both fistulas effected a significant decrease in blood pressure. The angiographic appearance of a renal AV fistula often reveals its cause. These fistulas can cause significant morbidity. A review of 49 cases of congenital renal AV fistulas reveals that most are found in women and in the right kidney. Bilateral renal AV fistulas have not been previously described. Hypertension commonly develops in patients with renal AV fistulas and may resolve or improve upon fistula ablation. Improvement in blood pressure after fistula ablation occurs more frequently in traumatic fistulas than in congenital ones. Although the pathophysiology of hypertension is felt to be the shunting of the blood flow by the fistula from the renal parenchyma and subsequent stimulation of the renin system, renal vein renin sampling may be of little diagnostic value.