With the growing epidemic of obesity, the incidence of both nonalcoholic fatty liver disease (NAFL) and nonalcoholic steatohepatitis (NASH) is increasing. The intestinal microbiota differs between individuals who are obese or have normal body mass indices. Animal studies have shown increased intestinal permeability in NAFL, NASH, and cirrhosis. This increases the risk of oxidative and inflammatory injury to the liver from intestinal microbacteria. It may also increase the risk of fatty acid injury and fatty deposition. Bacterial translocation is associated with increased portal hypertension and hepatic encephalopathy in cirrhosis. By preventing bacterial adhesion and translocation, probiotics may have a role in the management of patients with NAFL, NASH, and cirrhosis. Multiple small studies have suggested that probiotics improve some of the clinical markers of activity in patients with NAFL and NASH. Controlled studies have also shown improved outcomes in patients with cirrhosis who were treated with probiotics.