A model was designed to study the relation between urinary infection and vesicoureteral, low-grade, total reflux. Surgical alteration of the ureterovesical junction produced grade 2 vesicoureteral reflux in seven of 13 animals. In the other six animals, surgery had rendered the vesicoureteral junction marginally competent and chronic bladder infection caused grade 2 reflux. It was found that grade 2 vesicoureteral reflux in the adult monkey neither prolongs urinary tract infection nor causes continued renal infection.