In four patients, intra-abdominal abscesses were identified by ultrasonic technique: a right lower quadrant abscess in Crohn disease, a pyogenic liver abscess, a pelvic abscess following rejection and removal of a transplanted kidney, and a perinephric abscess. In all four the establishment by ultrasound that the mass was filled with fluid was critical in guiding drainage. Diagnostic ultrasound is a safe and effective means for the detection, localization, and characterization of retroperitoneal, intraperitoneal, or intraparenchymal inflammatory masses.