This lecture covers post-transplant lymphoproliferative disorders (PTLD) with a focus on the WHO 2017 classification. Diagnostic approach as well as risk factors for development of PTLD are covered. PTLDs are the best-delineated immunosuppression-related lymphoproliferations in the WHO 2017. Their classification can provide a framework for learners to understand other immunosuppression-related lymphoproliferations, and other EBV-related lymphoproliferative disorders.