The article presents a case study of a 21-year-old man with ulcerative colitis, sigmoidoscopic appearance and histology of colonic biopsy specimens. Cytomegalovirus (CMV) 65 pp antigenemia assays of the patient confirmed CMV viraemia and intravenous ganciclovir was administered. Cytomegalovirus pp 65 antigenemia became negative and the patient's colitis was resolved after four weeks of treatment.