Abscesses developing within the retroperitoneal spaces are serious surgical infections which are associated with prolonged morbidity and high mortality unless diagnosed early and treated adequately. These lesions are usually secondary, being complications of infections, injuries, or malignancy of adjacent retroperitoneal or intraperitoneal organs1-5; osteomyelitis of the vertebral column or 12th rib; suppurative lymphadenitis; or bacteremia. The frequency with which these abscesses have been seen in recent years, even though antibiotic therapy has been in widespread use, and the associated diagnostic and therapeutic problems presented by them have stimulated us to review our cases seen in the Department of Surgery of the Cincinnati General Hospital and University of Cincinnati. Relatively little attention has been given to the problem of retroperitoneal infections, and most published reports have been concerned with case presentations and short reviews.5-11 The review by Neuhof and Arnheim in 19447 is more comprehensive. Material The records