A prospective study of 21 patients with the diagnosis of non-alcoholic steatohepatitis (NASH) was carried out. All patients had hepatomegaly and in 10 (48%) image studies were consistent with steatosis and/or fibrosis. Biochemically, there was increase of AST, ALT and cholesterol in 48%, of GGT in 52% and of alkaline phosphatase in 38%. 18 patients were obese, 2 of them diabetic, 2 others had a history of exposure to drugs (amiodarone and isopropilic alcohol) and the last one presented hypothyroidism. Liver biopsies were studied using a semiquantitative scale to evaluate the degree of steatosis, inflammation and fibrosis in a scale from 1 to 3. Results showed a medium score of 2.6 for steatosis, 1.5 for inflammation and 1.8 for fibrosis. Four patients had cirrhosis and Mallory bodies were found in 11 cases (52%). NASH is an oligosymptomatic disease that can be found in different clinical conditions, mainly obesity, and is more frequent in women. It is histologically indistinguishable from alcoholic steatohepatitis. It is frequently underdiagnosed clinically and must be taken into account as a possible cause of cryptogenetic cirrhosis.