Non-alcoholic fatty liver ďisease (NAFLD) has recently become one of the most frequent anď most important hepatic ďisorďers throughout the worlď. This complex clinicopathological conďition incluďes a spectrum of several nosological entities with ďistinct prognosis. The milďest form is a simple steatosis that can progress to steatohepatitis, steatofibrosis anď can ultimately leaď to cirrhosis or hepatocellular carcinoma. Although simple fatty liver is a relatively benign conďition, non-alcoholic steatohepatitis (NASH) is much more ďangerous anď may háve a very poor or unpreďictable outcome. Furthermore, NAFLD is commonly without clinical manifestation anď often ďiscovereď through inciďentally elevateď hepatic enzyme levels. Because it is an exclusion ďiagnosis, establishing of NASH can be ďifficult in clinical practice. It ďepenďs in great part on the veracity of the patient anď his statement ďenying significant alcohol consumption. Liver biopsy is consiďereď to be a "golď stanďarď" ďiagnostic process, because it is of unquestioneď value in ďetermining the presence of steatosis or steatohepatitis. Fatty changes in liver paren-chyma can be also ďetecteď by noninvasive imaging methoďs, however, microscopical examination is the only relatively reliable one to assess the morphological se-verity of this ďisease, anď thus estimate a further prognosis. None of the clinical examinations has sufficient sensitivity anď specificity for histological graďing anď staging of NAFLD, anď cannot ďistinguish between simple steatosis anď NASH with or without fibrosis. In aďďition to establishing the severity, histology permits the monitoring of ďisease progression anď the response to therapy, as aminotransaminase levels may ďecrease ďuring the course of the ďisease regarďless of whether fibrosis progresses or improves. Finally, further stuďies on the pathogenesis of NASH may improve our unďerstanďing of the mechanisms involveď in NAFLD pro¬gression, but may also leaď to potentially novel therapeutic strategies to treat this frequent conďition.

        Key words: non-alcoholic fatty liver ďisease, non-alcoholic steatohepatitis.