We report a case of increased aspartate aminotransferase (AST, EC 2.6.1.1; GOT) in a 17-year-old girl which persisted for 3 years. The patient was healthy, but a high level of serum AST was detected during a school health check. Further examination revealed that AST was increased to as high as 259 IU/l while alanine aminotransferase (ALT) was normal. Immunoelectrosyneresis and immunoprecipitation methods revealed that this atypical AST combined with IgG--kappa, lambda globulin and formed macromolecular complexes. Including the present case, 26 cases of IgG-complexed AST have been reported. It is important to be aware of this syndrome, and thereby avoid unnecessary examinations and therapies.