Objectives: A variety of autoimmune conditions occur in association with primary biliary cirrhosis, Among these conditions are sicca syndrome, Raynaud's phenomenon, arthritis, and Hashimoto's thyroiditis, Information is sparse regarding the prevalence and natural history of these conditions when associated with primary biliary cirrhosis and their response to ursodeoxycholic acid treatment. We evaluated the prevalence, natural history, and response to ursodeoxycholic acid therapy of these conditions coassociated with primary biliary cirrhosis, Methods: One hundred-eighty patients with primary biliary cirrhosis, enrolled in a prospective randomized controlled trial of ursodeoxycholic acid (13-15 mg/kg/day), were included. Patients were assessed at study entry and annually. Results: At entry, 77/180 patients (33%) had one of the four conditions, and 18/180 patients (10%) had two or more conditions. Sicca syndrome was the most common, occurring in 58/180 patients (32%). After 2 yr, there was no difference between the treatment groups with regard to resolution or spontaneous onset of these autoimmune features. Sicca syndrome was the most common spontaneously developing condition (9% per yr), Sicca syndrome was the most common associated autoimmune condition, present in one-third of our patients. The associated conditions tended to improve over time? with a low rate of spontaneously developing these conditions. Although ursodeoxycholic acid therapy leads to improvement in the underlying liver disease, it did not appear to influence either the development or resolution of these autoimmune features. Conclusions: Although ursodeoxycholic acid is beneficial in the treatment of primary biliary cirrhosis, it had no measurable effect on the autoimmune conditions coassociated with the disease. (Am J Gastroenterol 1998;93:958-961, (C) 1998 by Am, Cell. of Gastroenterology).