OBJECTIVE: To determine the diagnostic value of antibodies against soluble liver antigen (anti-SLA antibodies) and a number of other antibodies for the diagnosis ofautoimmune hepatitis (AIH). DESIGN: Retrospective. METHOD: Anti-SLA, antinuclear antibodies (ANA), antibodies against smooth muscle (anti-SMA), anti-neutrophil cytoplasm antibodies (peri-nuclear pattern; pANCA) and antibodies against liver-kidney microsomal antigen type 1 (anti-LKM-1) were determined in the sera of 97 patients with AIH and 121 patients with other liver disorders including viral, drug-related and alcoholic liver disease. The sensitivity and specificity of each of the antibodies, or a combination ofantibodies, were calculated for the diagnosis 'AIH'. RESULTS: Anti-SLA antibodies were found only in AIH patients (specificity: 100%); 1 in 7 AIH patients (14%) had these antibodies and in 2% they were the only detectable antibodies. Anti-LKM-1 antibodies also showed a 100% specificity for AIH although the sensitivity was much lower (2%). Whilst the sensitivity of ANA (53%), pANCA (39%) and SMA (39%) was higher, the specificity of these antibodies for AIH was lower. 20% of AIH patients tested negative for all autoantibodies. The simultaneous presence of more than one antibody increased the probability of AIH diagnosis. CONCLUSION: When AIH is suspected, the presence of one or a combination ofanti-SLA, ANA, anti-SMA, anti-LKM-1 and pANCA antibodies is helpful for the often difficult differential diagnosis between AIH and other liver disorders. Anti-SLA antibodies are specific for AIH and appear to be a useful diagnostic parameter.