The invention relates to a method of diagnosing non-alcoholic steatohepatitis (NASH) using molecular markers. The inventive method consists in detecting and quantifying, in vitro in a hepatic tissue sample, the levels of a protein which can be used as a NASH molecular marker and which is selected from apolipoprotein A1, sub-unit .beta. of the mitochondrial ATPase, leukotriene A4 hydrolase, keratin 18, guanidine acetate N-methyltransferase, superoxide dismutase, albumin, antioxidant protein 2 (isoform 1), prohibitin 1, methionine adenosyl transferase, long-chain acyl CoA dehydrogenase, selenium binding protein, antioxidant protein 2 (isoform 2), and combinations of same. The invention further consists in comparing the results obtained with the normal values of said proteins in healthy hepatic tissue. Said method can be used to diagnose NASH and/or to assess a patient's potential risk of developing NASH.