The immunofluorescent method was used in a group of patients with primary biliary cirrhosis in order to detect antibodies against mitochondria and against smooth muscle tissue. All cases were found positive in the test for the presence of antimitochondrial antibodies. In the test for the presence of antibodies to act against smooth muscle tissue, positivity was found in 3 cases. Both tests are suitable auxilliary methods of investigation in diagnosing primary biliary cirrhosis.