A persistent increase in non-virus non-alcohol related aminotransferase levels can have multiple causes, which differ in terms of prevalence and clinical importance. In the general population, the most frequent cause is non-alcoholic hepatic steatosis, which can evolve into steato-hepatitis and cirrhosis. The treatment for steatosis and non-alcoholic steato-hepatitis consists of modifying lifestyles, whereas the effectiveness of drug treatment remains to be determined. Other much less frequent (yet not rare) causes of persistent non-virus non-alcohol related elevations in aminotransferase levels are celiac disease and hemochromatosis, whereas autoimmune hepatitis, primary biliary cirrhosis, primary sclerosing cholangitis, and alpha-1-anti-trypsin deficit are rare. Given that some of these conditions are susceptible to treatment, early diagnosis is important. No epidemiological data are available for evaluating the prevalence of elevated aminotransferase levels correlated with the toxicity of drugs or other xenobiotics, including herbal products. The present document, created by a panel of experts based on a systematic review of scientific evidence, is mainly geared towards physicians working in General Medicine and Transfusion Centres, who generally represent the first contact of persons with elevated aminotransferase levels. The document includes suggestions for diagnosing causes of persistent non-virus non-alcohol related increases in aminotransferase levels, considering the frequency and response to treatment. The conditions requiring specialized visits are also indicated.