Recombinant human interleukin 11 (rhIL-11) is a pleiotropic cytokine that stimulates bone marrow stem cells to proliferate and decreases intestinal mucosal injury produced by cytoablative drugs and radiation in animals. The effects of rhIL-11 were studied in a hamster model of oral mucositis and in two rat models of inflammatory bowel disease (IBD). Oral mucositis was induced in male Golden Syrian hamsters with 5-fluorouracil 60 mg/kg intraperitoneal, days 0 and 2. Peak mucositis occurred by day 10 in vehicle treated animals. rhIL-11, given twice daily subcutaneously, decreased the mucositis in a dose-dependent manner and increased animal survival at all doses tested. In two models of IBD, the acetic acid-induced acute colonic injury model in Sprague-Dawley rats and the transgenic Fischer 344 rats expressing human HLA-B27 and beta 2-microglobulin, rhIL-11 decreased the gross and microscopic damage in the colons of these animals. These data suggest that rhIL-11 exerts effects on the gastrointestinal mucosa which ameliorate responses to injurious stimuli.