Fatty liver is a very frequent pathologic condition of the liver. The main aetiological factors are: alcohol, metabolic disorders including obesity, diabetes mellitus, hyperlipidaemia, drugs and others. We present nonalcoholic fatty liver disease, which is a frequent complication of metabolic diseases and nonalcoholic steatohepatitis, which can lead to liver cirrhosis. The symptoms are uncharacteristic or lacking; the diagnosis is based on biochemical liver tests and liver visualization tools. Treatment of nonalcoholic fatty liver disease includes elimination of aetiological factors; some drugs play a supportive role. The disease should be thoroughly diagnosed, because if not treated it can lead to liver cirrhosis with further complications.