The prevalence of inflammatory bowel disease (IBD) in patients with PSC differs in various part of the world. Ulcerative colitis (UC) is most common, but 1 to 14% of all primary sclerosing cholangitis (PSC) patients have Crohn disease with colonic involvement. Many PSC patients without clinical symptoms of IBD have colonoscopic and histological findings compatible with IBD, and the subclinical phase may last several years before onset of symptoms of active colitis. The characteristics of UC in patients with PSC are different from those in UC patients without PSC. The colitis is usually substantial, the clinical course of the colitis is quiescent, and rectal sparing is common. Moreover, PSC patients with UC have a higher risk of developing colorectal dysplasia/carcinoma than UC patients without PSC. In patients having an ileal pelvic pouch with ileal anal anastomosis, PSC is a risk factor for development of pouchitis. It is important that all PSC patients with UC are included in colonoscopic surveillance programs.