Ulcerative colitis is one of the inflammatory bowel diseases that is increasing in incidence worldwide. The objective of this work was to evaluate the activities of the hydroethanolic extract of the leaves of Bixa orellana on colitis in rats. Thirty-six rats were anesthetized with ether after 18 hours of fasting and ulcerative colitis was induced by intrarectal administration of 1 mL of acetic acid (5%) in all animals except the normal control group which received instead distilled water (1 mL). 48 hours after induction, the normal control and the negative control received distilled water (10 mL/kg), the positive control received loperamide (5 mg/kg) and three test groups received hydroethanolic extract Bixa orellana leaves at 100, 200 and 400 mg/kg per day for seven days. Administration of the extract significantly (P <0.01) reduced the number of diarrheal stools, nitric oxide and malonedialdheide levels, anemia and the number of colon lesions. The extract significantly (P <0.01) improved body weight loss as well as antioxidant parameters (superoxide dismutase, catalase, gluthation). These results would justify the use of Bixa orellana in the treatment of inflammatory bowel disease.