Six patients on hemodialysis who had stenotic segments of failing arteriovenous fistulas underwent attempted dilatations with a Grüntzig balloon catheter. In three patients the dilatation was successful: two fistulas were still functioning at the time of this study (10 and 8 months), and one fistula functioned up to the patient's death (2 months). Dilatation was unsuccessful in two 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, and 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.