Anlgesic agents against visceral pain typically rely on a noxious chemical irritation of the peritoneum, e. g., acetic acid and phenylquinone writhing test. While useful, this type of assay depends upon an acute inflammation and the release of local alogens. Further, ethical and scientific constraints prevent repeated assessments in a single animal, thereby compounding the difficulty of assessing tolerance development to analgesic agents. To overcome these constraints, Colburn et al. developed a model for mechanical visceral pain model (VPM) based on a repeatable and reversible duodenal distention in the rat. A chronic indwelling intraduodenal balloon catheter is well tolerated and upon inflation produces a writhing response graded in proportion to distention. This response is inhibited by morphine in a dose dependent manner. We found that a model for visceral pain was thought to be a great value.