Herpes virus infection leads to severe and fatal disease in individuals with suppressed immunity. In patients with inflammatory bowel disease (IBD), particularly those with ulcerative colitis (UC), those undergoing immunosuppressive therapy, or those unresponsive to medical therapy, cytomegalovirus (CMV) has been found to be associated with significant clinical morbidity. In addition, other herpes viruses, particularly human herpes virus 6 (HHV‑6) and Epstein-Barr virus (EBV), have been identified recently in the colonic mucosa of individuals with IBD, although the relationship between herpes virus infection other than CMV and exacerbation of IBD remains unknown. In this review, we discuss herpes virus infection in patients with UC, focusing on the prevalence and diagnosis of CMV infection as well as the prevalence of single or mixed infection with herpes virus (HHV‑6 and EBV) in addition to CMV. Moreover, significance of genotyping of CMV in UC is discussed.