Analysis of rodent models of inflammatory bowel disease, airways hyper-reactivity, diabetes, and multiple sclerosis has shown that infection with helminth parasites can significantly reduce the severity of the disease. Here, we assessed whether rats infected with the tapeworm Hymenolepis diminuta were protected from gastric ulceration induced by the serosal application of acetic acid. All rats gavaged with infective cysticercoids harbored adult worms when assessed 6 wk later, and acetic acid evoked the expected gastric ulceration. However, infection with H. diminuta did not affect the degree of gastric ulceration at either 3 or 7 days post-acetic acid application, as gauged by ulcer area or histopathology. While the data do not dismiss the possibility that infection with other helminths could be anti-ulcerogenic, they illustrate that 'helminth therapy' for inflammatory disease is likely to be both disease- and helminth-specific.