In a 13 year retrospective study mitochondrial antibodies were found in 1.71 p. 100 of patients about 60 years old with a strong female predominance. The presence of these antibodies was associated with a significantly increased level of the three classes of immunoglobulin and a marked cholestatic syndrome. In 76.9 p. 100 of cases the antibodies were associated with hepatic disease, mainly of immunological origin (67.7 p. 100). Primary biliary cirrhosis was the most frequent with significantly increased levels of mitochondrial antibodies, immunoglobin M, alkaline phosphatase and cholesterol. However, there was no correlation between the antibody levels and the clinical, biological and histological stages, thus ruling out any prognostic significance. The use of human cultured cells in the antibody detection assay increased the positivity of antinuclear antibodies compared with assays using classical rat liver substrates. Six sera were positive for anticentromere antibodies: 5/6 showed signs of the CRST syndrome with a primary biliary cirrhosis in 3/5 cases. The frequency of the association of primary biliary cirrhosis and other autoimmune diseases supports the results of previous reports as well as the finding of an association between mitochondrial antibodies and other auto-antibodies. In 3 cases primary biliary cirrhosis was associated with a chronic pancreatitis, suggesting a pluriglandular sicca syndrome, and in 3 other cases with a monoclonal IgA gammopathy. Mitochondrial antibodies are associated with other auto-immune non-hepatic diseases in 15.4 p. 100 of cases. The presence of increased levels of mitochondrial antibodies without any other auto-antibody associated with a chronic non-surgical cholestasis and an increased level of immunoglobulin M is still strongly suggestive of primary biliary cirrhosis.