Background: Myocarditis is an inflammatory heart disease and in acute phase LV function is seriously disordered. This results in severe heart failure and sometimes is fatal. In rat model, experimental autoimmune myocarditis(EAM) resembles human giant cell myocarditis. In cardiomyocyte from EAM rat heart,various gene expressions are changed as compared with normal rat and it seems to be associated with LV disorder. Purpose: The aim of this study is to demonstrate mRNA expressions in the cardiomyocyte of EAM rat and evaluate difference between normal and EAM rat. Method: Normal and EAM adult rat hearts were removed, and cardiomyocytes were isolated after Langendorff perfusion apparatus and enzymatic digestion of the hearts. Then total RNA from cardiomyocytes was extracted and used for analysis of gene expression. Analysis was performed by using oligonucleotide microarrays(DNA chip). Result: Microarrays analysis data showed about 7000 gene expressions and fold induction or fold reduction in expression of gene specific mRNAs between two samples. Many gene expressions were changed between EAM rat with normal in cytoskeletal, signal transduction, ion transport,muscle contraction protein and unkown protein. Conclusion: Some of genes indicated the difference between normal and EAM rat may be related to LV disorder in myocarditis.However further study will be needed in the future.