OBJECTIVE: Nitric oxide (nitric, oxide, NO) plays a dual role.On the one hand, it can inhibit inflammatory process under physiological conditions, and on the other hand, a large amount of NO can be involved in inflammation in autoimmune myocarditis.This study aimed to investigate the effects of N-nitro-L-arginine methyl ester (L-NAME), a kind of inducible nitric oxide synthase (iNOS) inhibitor, in the treatment of Balb/C mice with experimental autoimmune myocarditis (EAM) and to discuss the therapeutic mitochondrial mechanism induced by apoptosis.