AIM: To investigate the role of expression of peroxisome proliferator-activated receptor ?(PPAR ?) in pathogenesis of rat fatty liver.METHODS: The rats were treated with a low dose of carbon terachloride (CCl 4) and fed a high fat diet to produce fatty liver. We determined the concentrations of triglyceride (TG), total cholesterol (TC), free fatty acid (FFA) in liver and the alanine aminotransferase (ALT) activity, tumor necrosis factor-? (TNF-?), FFA in serum and the degree of hepatocytic steatosis. Total RNA of liver was extracted, and the expression of PPAR ? were analyzed by semi-quantitative RT-PCR method. RESULTS: In model group, the hepatocytic PPAR ? mRNA expression decreased to 0 41?0 28, compared to 1 41?0 29 in the control group ( P