We report three patients in whom arteriovenous fistulas probably occurred following placement of central venous catheters. Two fistulas apparently followed internal jugular vein catheterization (or attempts), and one was demonstrated angiographically following subclavian vein cannulation. One fistula was repaired operatively, and in this case two separate fistulas in the same anatomical region were found. One patient refused surgery but remained asymptomatic after 6 months of follow-up. In the third patient the fistula probably spontaneously disappeared within one week of its appearance. We discuss two methods of central vein cannulation which should decrease the occurrence of complications following the procedure.