There is a growing appreciation of the increased risk for malignancy following solid organ and hematopoietic stem cell transplantation as the survival of these patient populations increases overall. The risk for malignancy is related to a complex interaction of type, degree, and duration of immunosuppression, viral status, and recipient age. Most of the malignancies documented are common in the general population but occur with increasing incidence and have significant implications for post-transplant surveillance. Post-transplant lymphoproliferative disorder is specific to the transplant population and remains a treatment challenge. The development of novel immunosuppressive agents, the use of individualized immunosuppressive regimens, and collaborative therapeutic trials are necessary to advance clinical care for these patients. This article will review the current issues around malignancy in the post-transplant patient population.