Six patients on hemodialysis who had stenotic segments of failing arteriovenous fistulas underwent attempted dilatations with a Gruentzig balloon catheter. In 3 patients the dilatation was successful: 2 fistulas were still functioning at the time of this study (10 and 8 mo.) and 1 fistula functioned up to the patient''s death (2 mo.). Dilatation was unsuccessful in 2 patients because the stenosis located adjacent to the arteriovenous anastomosis could not be approached with the balloon. There were no complications secondary to the technique. The dilatation attempt did not preclude surgical revision when it failed. This technique, which can be performed in ambulatory patients, provides an alternative to surgical revision of the failing arteriovenous fistula.