Following the seminal publication by the group from Milan, Italy using a restrictive set of criteria for orthotopic liver transplantation in patients with hepatocellular carcinoma to limit the risk for tumor recurrence, excellent 5-year patient survival of greater than 70% after liver transplantation has been reported from many centers using criteria similar to or slightly exceeding the Milan criteria (single lesion of </=5 cm, or 2-3 lesions of </=3 cm). The growing experience and success of orthotopic liver transplantation for HCC have also fueled controversies related to expansion of conventional criteria for cadaveric or living-donor liver transplantation based on tumor size and number. The limitations of imaging studies, exemplified by tumor under-staging in up to 25% of patients,have been a major concern for liberalizing the current criteria for liver transplantation. The University of California, San Francisco criteria (single lesion of </=6.5 cm, or 2-3 lesions of </=4.5 cm with a total tumor diameter </=8 cm) have been independently tested in several studies, and undergone prospective evaluation based on preoperative imaging. This article provides an in-depth review of published data on expansion of current criteria for liver transplantation.