Early experiences in transplantation, which pre-dated brain death laws, utilized organs from donors with active malignancies. [1,2] The use of organs from such donors occasionally resulted in the transmission of malignancy from the donor to an unknowing recipient. Over a period of three decades, Israel Penn, M. D. catalogued some two hundred and fifty cases of organs transplanted from donors with a history of malignancy; carefully examining each reported case for tumor histology, donor risk factors, method of tumor presentation and recipient outcome. [1-3] Some recipients never developed malignancies, while others were less fortunate, developing cancers that were suspicious for donor origin. The evolution of transplantation has resulted in improved patient survival, which in turn has led to an increased demand for organ transplantation. Unfortunately, the supply of organs available for transplantation has failed to keep pace with the demand, with the worldwide deficit growing annually. In an effort to bridge the widening gap, utilization of older and more marginal donors has been suggested. [4] However, use of older donors is accompanied by the likelihood that a significant proportion may have undiagnosed malignancies. [2,5] Multiple transplant programs have considered the use of donors with tumors of non-malignant or even low-grade malignant histology, most often involving the central nervous system (CNS). [6] According to a survey from the United Network for Organ Sharing (UNOS), central nervous system malignancies are among the most commonly identified malignancies found in potential donors. [7,8] This study examines the distribution of potential donor transmitted malignancies reported to the Israel Penn International Transplant Tumor Registry. The incidence of tumor transmission is examined in the overall group as well as among individual histologies. We also seek to identify specific factors associated with the risk of malignancy transmission from donor to recipient, in an effort to minimize future transmission of donor tumors to unwitting recipients. The study is based on voluntary registry data, which some argue can be criticized for a lack of true incidence data. In reality, however, this data may provide a more accurate insight since it is based on transmissions from high-risk donors rather than from the general population.