Ursodeoxycholic acid (UDCA) was administered to 10 patients diagnosed as having primary biliary cirrhosis (PBC) after liver biopsy. Eight patients were anicteric, and two were icteric cases. One patient was in stage I, seven were in stage II, one in stage I-III, and one in stage III-IV of Scheuer's classification. Six hundred milligrams of UDCA were administered orally after meals three times daily to all of the patients for more than 1 yr. The period of UDCA administration ranged from 6 to 41 months. The major findings are as follows: 1) in six out of seven patients with pruritus, itching disappeared 1 month after administration of UDCA; 2) both serum alkaline phosphatase and gamma-glutamyltranspeptidase levels began decreasing significantly the first month after the onset of UDCA treatment, and continued decreasing throughout the treatment; 3) GOT and GPT levels also decreased significantly during the administration of UDCA, compared with before-treatment levels; 4) in one icteric patient with portal hypertension, although serum biliary enzyme levels improved after treatment, serum bilirubin level got worse, and the patient died of esophageal variceal hemorrhage. In another icteric case, biliary and bilirubin levels improved slightly after treatment; 5) antimitochondrial antibody titer decreased in four cases, but IgM levels and other immunological parameters were not changed; 6) serum UDCA increased significantly during UDCA treatment; in particular, glyco-UDCA occupied up to 40% of the total bile acid and CDC decreased to 25%; 7) portal inflammation activity decreased in all five patients who had undergone follow-up liver biopsy, more than 1 yr after UDCA administration--bridging fibrosis decreased in three cases; and 8) no side effects were observed in any of the cases. Although large-scale, randomized, controlled, double-blind tests are necessary, it is speculated that the long-term administration of UDCA is a safe and effective treatment for the improvement of biliary enzyme levels and pruritus in anicteric PBC.