Betaine prevents hepatic damage caused by ethanol and carbone tetrachloride (CCl4) in rats. Present study was to investigate the effect of betaine on the hepatic microsomal triglyceride transfer protein (MTP) mRNA expression in orotic acid (OA)-induced fatty liver in rats. OA feeding was attributed to the significant increase in the hepatic levels of triglyceride and the serum levels of ALT and AST and resulted in typical histology of fatty liver contained numerous largely fat droplets. While concomitant supplementation of betaine to OA diet was slightly reduced the hepatic triglyceride concentrations and was significantly decreased ALT activity. Hepatic MTP mRNA expression by OA treatment increased by 14% despite triglyceride accumulation in the liver in OA treatment rats relative to rats fed a normal diet without OA supplemented, but MTP expression by simultaneous supplementation of OA and betaine was slightly decreased by 7.9% as compared to the OA-feeding rats. A significant elevation of TBARS contents in the liver homogenate, microsome, and mitochondrial fractions of the OA-feeding rats compared with the normal rats, however, these increases were significantly or slightly decreased by simultaneous addition of OA and betaine. The increases of hepatic OA and betaine levels in OA feeding rats was also found when compared to the normal rats, but these increases were significantly lowered in the concomitant supplementation OA and betaine. The content of Fe was significantly increased in the OA feeding rats, but this elevation showed significantly recovered as low as the normal level by concomitant with OA and betaine. Zinc content was also significantly decreased in the OA feeding rats compared with the normal rats, but this reduction was more significantly elevated by concomitant with OA and betaine. Hepatic glutathione content in the OA feeding rats was similar to that of the normal rats, but this content was slightly reduced without statistically significant differences. But, a significant elevation in the hepatic glutathione content was found in the simultaneously administration OA and betaine. The hepatocytes contained numerous largely fat droplets induced by OA administration and was slightly reduced by simultaneous supplementation of OA and betaine. Present study demonstrated that betaine has a weak preventive action on the OA-induced triglyceride accumulation.