The report describes a rare case of an iatrogenic arteriovenous fistula of the vertebral artery to the vertebral vein which arose after insertion of a central venous catheter via the jugular vein. We give special attention to the role of colour duplex sonography in the primary diagnosis of such fistulas. As can be seen from published reports with this non-invasive examination, the diagnosis of fistulas could not be established in all cases, where an abnormal communication between the vessels was later revealed by angiography. The most probable reason is the particular feature of the anatomical course of the vertebral artery which in its middle third is protected in a bony canal through the foramina transversaria of the cervical vertebrae and can be only partially visualised by sonography. Consequently only fistulas in the visible parts of the artery can be detected by sonography. In our case the most important criteria of duplex sonography for an arteriovenous fistula were fulfilled and the diagnosis was confirmed by angiography. This procedure with primary use of colour duplex sonography and additional clarification of uncertain findings by angiography, seems to be reasonable if the symptoms are compatible with the diagnosis of an arteriovenous fistula of the neck vessels.