Barium sulfate is universally used contrast media in gastrointestinal roentgenology, and spillage of barium into peritoneal cavity can occur. The references on effect of barium sufate in the peritoneal cavity have been scattered and the results are varied. In 80 rats, body wights of 130gm to150gm, sterile pure barium, sterilecommercial barium, intestinal content, and mixed pure barium and intestinal content were experimentally injectedinto the peritoneal cavity. Consecutive weekly laparotomy and microscopic examination were done for 4 weeks. The results are as followings; 1. Mild inflammatory reaction and mild adhesion after sterile purebarium injection. 2. Mild inflammatory reaction and moderate adhesion after sterile commercial barium injection. 3. Acute peritonitis and abscess formation after intestinal content injection. 4. High mortality due to severe acute peritonitis, and severe adhesion in survivors after injection of both pure barium and intestinal content.