Renal abscesses are misdiagnosed often and, consequently, mistreated or treated too late. Forty cases of renal abscesses divided into anatomic categories--perinephric, renal cortical, and corticomedullary--are reviewed. Various conditions seem to predispose to renal abscesses: urinary tract infections, vesicoureteral reflux, calculi, or other medical problems. This retrospective study discloses that a high correlation exists between organisms found in the patients' urine cultures and those organisms cultured from all 3 categories of abscesses. Accurate and complete urine bacteriologic study is therefore an essential tool for diagnosis.