Iatrogenic arteriovenous fistula is the second most frequent complication in endovascular procedures, often demanding surgical treatment. Contrary to pseudoaneurysm, arteriovenous fistula appears rather infrequently and still less frequently it is properly identified in medical examination and diagnostic imaging. It follows peripheral vascular procedures in 0.005-0.14% [1] and cardiologic procedures in 0.3-2.8% of cases [2-6]. The paper presents principles of arteriovenous fistula diagnostics and an outline of its treatment.