CD4+ CD25+ regulatory T cells have been shown to prevent T cell-mediated immune pathology; however, their ability to ameliorate established inflammation has not been tested. Using the CD4+ CD45RB high T cell transfer model of inflammatory bowel disease, we show that CD4+ CD25+ but not CD4+ CD25− CD45RB low T cells are able to cure intestinal inflammation. Transfer of CD4+ CD25+ T cells into mice with colitis led to resolution of the lamina propria infiltrate in the intestine and reappearance of normal intestinal architecture. CD4+ CD25+ T cells were found to proliferate in the mesenteric lymph nodes and inflamed colon. They were located between clusters of CD11c+ cells and pathogenic T cells and found to be in contact with both cell types. These studies suggest that manipulation of CD4+ CD25+ T cells may be beneficial in the treatment of chronic inflammatory diseases.