Ultrasonographic findings in nine cases of peritoneal mesothelioma are presented. The most common findings were sheet-like or nodular peritoneal thickening, soft tissue masses, fixation of the intestinal loops, mesenteric thickening, and minimal ascites which was disproportional to the degree of tumor dissemination. The authors found that abdominal sonography, using 3.75-7.5 MHz transducers, is a useful imaging method for diagnosis of peritoneal mesothelioma in high-risk groups.