In the past decade, subureteric endoscopic injection of Teflon or collagen has been propagated as a safe and successful treatment for vesicoureteral reflux. In our center, from 1990 through 1995, 118 children and 5 adults with reflux and recurrent urinary tract infections were injected with cross-linked bovine collagen in an open, prospective study. Efficacy and safety were assessed 6 and 12 months after injection, and long-term (> or =3 years) results were available in 78 cases. The overall success rate was 58% (64% of ureteral units) free from reflux at 12 months and 54% (58%) after 3 years. Analysis of anatomic, urodynamic, and technical features showed the grade of reflux to be the best predictor of success or failure. When only primary low- and middle-grade reflux, without concomitant anatomic disorders, is considered, the long-term success rate rose to 69% (74% of ureteral units). In conclusion, subureteric collagen injection cannot ultimately replace the highly effective surgical reimplantation. However, the procedure offers a minimally invasive alternative in selected cases of mild reflux when conservative management is inadequate.