Eighty-seven patients with the clinical suspicion of an intraperitoneal abscess were examined by computed tomography. In 83 of these patients CT gave true positive or true negative results in reference to the diagnosis of local intraperitoneal fluids. The final diagnosis confirmed 28 abscesses in 26 patients. Most of these abscesses were in the left subphrenic space, the right subphrenic space, the right anterior subhepatic space, and the pelvis. The morphological criteria for intraperitoneal abscesses, shown by CT, are defined. Direct signs include form, impression on nonintestinal organs, density value, gas collection, pyogenic membrane, and infiltration in surrounding tissue. Indirect signs include ascites and pleural effusion and/or pulmonary infiltration. Differential diagnostic problems of intraperitoneal abscesses are discussed.