Malignant tumors are a significant cause of long-term morbidity and mortality in allograft recipients. Most solid tumors in transplant recipients are assumed to arise de novo in the setting of chronic immunosuppressive therapy; however, there have been instances in which malignant tumors have been transplanted in donated tissue from apparently healthy donors. We report a case of a 49-year-old liver transplant patient who presented with metastatic melanoma 9 months after transplantation for hepatocellular carcinoma and who later succumbed to the disease. To investigate the possibility that melanoma was derived from the donor liver, we used a commercially available polymerase chain reaction-based microsatellite marker assay to perform tissue identity testing. The genetic profiles of the patient's original hepatocellular carcinoma and the melanoma from the autopsy specimen were compared with the profile of the normal donor liver tissue, which was still available for testing. The pattern of microsatellite allelic expression strongly suggested that the melanoma detected at autopsy originated from the transplanted liver.