Although the technique of subureteral injection has been widely accepted as an alternative to reimplantation in the treatment of vesicoureteral reflux, the choice of the material to be used is controversial. We have used glutaraldehyde cross-linked bovine collagen to correct vesicoureteral reflux within the context of a Food and Drug Administration approved investigational study. We report the local tissue reaction to the implanted collagen in 7 patients who underwent reimplantation 3 to 19 months after failed endoscopic therapy. Glutaraldehyde cross-linked bovine collagen engendered a minimal localized inflammatory reaction without causing granuloma formation. Subsequent reimplantation was not hindered by the presence of the implant materials.