Computed tomography (CT), ultrasound, and 111In-labeled leukocyte scans are all used in the evaluation of abdominal abscesses. In this study, 170 patients in whom one, two, or all three of these modalities were used retrospectively reviewed. Diagnostic accuracy of 96% for CT, 90% for ultrasound, and 92% for 111In leukocyte scans was achieved. It was often necessary to use more than one modality to arrive at a correct diagnosis. The advantages and disadvantages as well as the causes for false positive or false negative interpretations of each of these modalities are reviewed. Analysis of the different examinations resulted in a suggested sequence by which patients can be examined, based upon their clinical condition. Patients who are not critically ill and/or who have no localizing signs should be studied first with 111In-labeled leukocyte scans. If, however, localizing signs should or the patient's condition necessitates prompt intervention, CT or ultrasound should be the first study performed.