Despite improved short-term outcome in patient and graft survival in renal transplantation, no major improvements have been detected in long-term survival. The success of solid organ transplantation lies in the administering an adequate dosage of an agent while at the same time avoiding toxicity related to excessive immunosuppression or concentrationrelated secondary toxicities to a large degree. Therapeutic drug monitoring would make it possible to define the therapeutic and toxic dosage ranges. We herein present an article concerning therapeutic drug monitorization of immunosuppressive drugs that are currently used in renal transplantation.