AIM: To develop a novel model of colitis in rats, using a combination of iodoacetamide and enteropathogenic E. coli (EPEC), and to elucidate the pathophysiologic processes implicated in the development of ulcerative colitis (UC). METHODS: Male Sprague-Dawley rats (n = 158) were inoculated intrarectally on a weekly basis with 4 different combinations: (a) 1% methylcellulose (MC), (b) 100 μL of 6% iodoacetamide (IA) in 1% MC, (c) 200 μL containing 4 × 108 colony factor units (CFU) of EPEC, and (d) combined treatment of (IA) followed by bacteria (B) after 2 d. Thirty days post treatment, each of the four groups was divided into two subgroups; the inoculation was stopped for one subgroup and the other subgroup continued with biweekly inoculation until the end of the experiment. Colitis was evaluated by the clinical course of the disease, the macroscopic and microscopic alterations, activity of myeloperoxidase (MPO), and by TNF-α gene expression. RESULTS: Findings indicative of UC were seen in the combined treatment (IA + B) as well as the IA conti-nued treatment groups: the animals showed slow rate of increase in body weight, diarrhea, bloody stools, high colonic ulcer score, as well as histological altera- tions characteristic of UC, with an extensive inflamma- tory reaction. During the course of the experiment, the MPO activity was consistently elevated and the TNF-α gene expression was upregulated compared to the control animals. CONCLUSION: The experimental ulcerative colitis model used in the present study resembles, to a great extent, the human disease. It is reproducible with characteristics indicative of chronicity. AIM: To develop a novel model of colitis in rats, using a combination of iodoacetamide and enteropathogenic E. coli (EPEC), and to elucidate the pathophysiologic processes implicated in the development of ulcerative colitis (UC). METHODS: Male Sprague-Dawley rats (n = 158) were inoculated intrarectally on a weekly basis with 4 different combinations: (a) 1% methylcellulose (MC), (b) 100 μL of 6% iodoacetamide 4 × 108 colony factor units (CFU) of EPEC, and (d) combined treatment of (IA) followed by bacteria (B) after 2 d. Thirty days post treatment, each of the four groups was divided into two subgroups; the inoculation was stopped for one subgroup and the other subgroup continued with biweekly inoculation until the end of the experiment. expression. RESULTS: Findings indicative of UC were seen in the combined treatment (IA + B) as well as the IA conti-nued treatment groups: the animals showed slow rate of increase in body weight, diarrhea, bloody stools, high colonic ulcer score, as well as histological altera- tions characteristic of the UC, with an extensive inflamma- tion reaction. During the course of the experiment, the MPO activity was consistently elevated and the TNF-alpha gene expression was upregulated compared to the control animals. CONCLUSION: The experimental ulcerative colitis model used in the present study resembles, to a great extent, the human disease. It is reproducible with characteristics indicative of chronicity.