Patients with cholestatic liver function tests and histological features of primary sclerosing cholangitis (PSC) but without the typical cholangiographic changes are considered to have small-duct PSC. The incidence of small-duct PSC and the natural history still is not known. We performed a retrospective search for patients diagnosed with small-duct PSC between January 1997 and December 2003. The diagnosis of small-duct PSC was based on biochemical features of chronic cholestasis, liver biopsy findings consistent with PSC, and a normal cholangiogram on endoscopic retrograde cholangiography. Six patients fulfilled the diagnostic criteria for small-duct PSC. All patients received medical therapy. After a mean follow-up time of 26.0 ± 29.8 months (range, 7–84 months), all patients are alive. Repeated liver biopsy was performed in one patient, 58 months after the initial one, and disclosed amelioration of histological findings (reduction in the Ludwig fibrosis score from 4 to 2). During follow-up symptoms disappeared in all patients who were symptomatic at diagnosis; none of those who were asymptomatic at diagnosis developed symptoms. At the time of last follow-up all patients showed significant improvement of their biochemical variables compared to baseline. Administration of aminosalicylates seemed to be of benefit irrespective of the presence of inflammatory bowel disease. No patients underwent liver transplantation or developed cholangiocarcinoma. Even though our study included a low number of patients and the follow-up time was relatively short, we can suggest that small-duct PSC rarely progresses to large-duct PSC and does not seem to be associated with development of cholangiocarcinoma. It thus seems to represent a separate entity with a favorable prognosis.