 Recently, it was elucidated that disruption of EP4 gene, which is one of PGE receptors, caused severe colitis in mice. Moreover, EP4-selective agonist AE1-734 was also revealed to ameliorate severe dextran sodium sulfate-induced colitis in mice. We therefore examined the effects of 2 weeks intravenous EP4-selective agonist therapy for patients with mild to moderate ulcerative colitis. 