An association between primary sclerosing cholangitis (PSC) and chronic ulcerative colitis (CUC) is well known in Western countries, but there have been no reports on this association in Japan. We reviewed 163 consecutive CUC patients (91 males and 72 females) diagnosed from 1984 to 1990 at Tokyo Women's Medical College. Abnormal liver function tests were found in 42 patients with CUC (25.8%), but chronic liver disease was only diagnosed in seven patients (4.3%). Among these seven patients, there were four with PSC, one with small-duct PSC, one with transfusion-associated chronic hepatitis and one with Type B liver cirrhosis. No relationship was found between the documented colonic manifestations of CUC and the presence of PSC. The four PSC patients did not have a longer history of CUC at the time of diagnosis of PSC than CUC patients without PSC. At the time of PSC diagnosis, two patients were asymptomatic, one presented with right upper quadrant pain, and the other had fatigue. Three patients were diagnosed as having CUC before the onset of PSC (range 2-13 years), and the other patient had both diseases simultaneously. All four had a good prognosis. Thus PSC was the most common chronic liver disease associated with CUC in our series, and it was present in all our CUC patients with alkaline phosphatase levels exceeding twice the upper limit of normal and mild transaminase elevation.