Ouchterlony immunodiffusion and ELISA were used for the detection of antimitochondrial antibodies. The results were compared with those of immunofluorescence measurements. The occurrence of antimitochondrial antibodies was investigated in 20 patients with primary biliary cirrhosis, in 30 with autoimmune disease and in 28 with porphyria cutanea tarda. Sonicated rat liver mitochondria fractions were used as antigens. Among the patients with primary biliary cirrhosis, Ouchterlony immunodiffusion revealed antimitochondrial antibodies in 18 cases, whereas antibodies were not found in the other groups of patients, except for 1 case of systemic lupus erythematodes. ELISA demonstrated that in all 20 patients with primary biliary cirrhosis where immunofluorescence revealed antimitochondrial antibodies, there was an increase in the quantity of antibodies against mitochondrial inner membrane fractions, and in 7 cases even against the outer membrane fractions. These 7 were the most serious cases clinically. These methods allow the differentiation of antimitochondrial antibody subtypes and promote the establishment of the diagnosis.