PBC is a chronic cholestatic liver disease, predominantly of women, in which interlobular and septal bile ducts undergo inflammation and destruction. Once initiated, the disease persists and progresses at varying rates. Neither the initiating nor perpetuating mechanisms are well understood. Current concepts of pathogenesis include (1) destruction of bile ducts is maintained and perhaps initiated by autoimmune mechanisms; (2) hydrophobic bile acids which accumulate in serum and liver cause functional and cytotoxic liver injury; (3) cytokines and lymphokines released at sites of inflammation may contribute to cell damage and fibrosis. A considerable body of evidence indicates that UDCA when fed orally leads to improvement in liver tests, in pruritus and in liver histology. There exist differences in opinion as to whether development of complications of liver disease, liver transplantation or transplant-free survival is affected. UDCA, a relatively non-toxic bile acid, when administered orally, alters the composition of the bile acid pool in factor of its enrichment with UDCA and appears to protect against the cytotoxic effects of endogenous bile acids that accumulate as a result of bile acid destruction. MTX is being shown to improve liver tests, symptoms and liver histology in a small number of precirrhotic patients with PBC. The mechanism of action is unknown but felt to be related to anti-inflammatory immunosuppressive effects of MTX. The current trial explores whether MTX improves the therapeutic effects of UDCA in PBC. Patients with PBC whose serum bilirubin is less than 3 mg%, who have been on UDCA for at least 6 months, and who satisfy a series of inclusion and exclusion criteria are stratified into 2 groups on the basis of liver histologic stage (Ludwig classification), i.e., early (Stages I and II) versus late (Stages III or IV). They are then randomized to receive either methotrexate or its placebo as a second drug while continuing to receive UDCA. The relative value of the two treatment arms is assessed by comparing their effects on symptoms, results of laboratory tests, development of complications of liver disease, histologic changes in liver, liver transplantation, and on transplant-free survival. The safety of each therapeutic regimen is also being determined.