Five cases of retroperitoneal iliac fossa abscess are presented. Abnormal excretory urogram and plain films, coupled with a history of either hip pain, limp, or pelvic mass should suggest the diagnosis. The excretory urogram is the most sensitive means of detecting iliopsoas abscess; all patients had medial displacement on the distal ureter. The upper urinary tract was normal in all cases. Study of the gastrointestinal tract may be of additional help in localizing the abscess and ruling out other pathology. A retroperitoneal muscle splitting approach is the preferred surgical procedure. Drainage of the abscess cavity and systemic antibiotic coverage are curative.