Mesothelioma are infrequenctly encountered tumors that aries from the surface of any mesothelial lined body cavity. They are found most often in the pleural cavity, less frequently in the peritoneal cavity, and much less frequently in the pericardial cavity or arising form the tunica vaginalis. Tumors are most malignant and usually are detected late in their course when they begin to interfere with organ function. Most noninvasive diagnostic efforts are not helpful. The radiographic appearance is nonspecific and so, diagnosis is commonly made by laparoscopy and laparotomy. We experienced 4 cases of 2 malignant and 2 benign peritoneal meothelioma which were no evidence of asbestose exposure. And, we believe that one case of malignant mesothelioma may be a consequence of prior radiation therapy.