Approximately 20% to 30% of patients undergoing liver transplantation for autoimmune hepatitis (AIH) develop features of recurrent disease. Diagnostic criteria for recurrent AIH are similar to those used in the nontransplanted liver and include, in varying combinations, biochemical, serological, and histological abnormalities and steroid dependency. However, these criteria are more difficult to apply in the liver allograft because of potential interactions between recurrent AIH and other complications of liver transplantation, particularly rejection, and the uncertain effects of long-term immunosuppression. In the absence of other reliable diagnostic markers, a number of studies have used the histological finding of chronic hepatitis as the main or sole criterion for diagnosing recurrent AIH. However, this also lacks diagnostic specificity because there are many other possible causes of chronic hepatitis in the liver allograft. In addition, approximately 20% to 40% of biopsies performed on patients as part of routine annual review have histological features of chronic hepatitis, for which no definite cause can be identified. Risk factors that have been associated with the development of recurrent AIH include suboptimal immunosuppression, HLA phenotype, disease type and severity in the native liver, and duration of follow up. In many cases in which recurrent AIH seems to be related to underimmunosuppression, biochemical and histological features rapidly resolve once adequate immunosuppression is restored. However, in other cases, recurrent AIH behaves more aggressively, with progression to cirrhosis and graft failure. Areas that require further study include developing uniform criteria for the diagnosis of recurrent AIH, identifying risk factors for severe recurrent disease, and determining optimal levels of immunosuppression that minimize the impact of disease recurrence without exposing patients to the risks of overimmunosuppression.