We determined the optimal conditions for the detection of anti-mitochondria antibodies by an enzyme linked immunosorbent assay (ELISA). Pig heart mitochondria was used at 5 mg/ml to coat polystyrene microplates and a serum dilution of 1/200 to carry out testing. This procedure detects anti-M1, M2, M4 and M6 antibodies and is more sensitive than indirect immunofluorescence. Anti-endoplasmic reticulum and anti-ribosome antibodies give negative results but anti-ds-DNA at high titres are a possible cause of false positivity.