A patient with intrarenal arteriovenous fistula and the development of severe diastolic hypertension following percutaneous renal biopsy is presented in detail. The fistula was discovered by auscultation of the flank area and demonstrated by arteriography. Studies for renal underperfusion were unconclusive. The hypertension was cured by nephrectomy. The possibility of an arteriovenous fistula should always be suspected when a post-renal biopsy patient develops unexplained hypertension.