 Ciclosporin A CsA is an immunosuppressive drug used in organs and tissues transplantations kidney, heart, liver, bone marrow ... to prevent rejection, and in different autoimmune or inflammatory diseases. A therapeutic drug monitoring TDM is required during a CsA treatment. It is justified by a narrow therapeutic range between efficiency and nephrotoxicity, and by large intra- and interindividual pharmacokinetic variability. TDM of CsA is conventionally performed by determining residual concentration, and sometimes concentration at 2 hours after administration. TDM of CsA is currently performed by venous sampling on ethylenediaminetetraacetic acid EDTA. Dried blood spot DBS sampling could be a particularly interesting alternative to conventional blood sampling. With DBS, capillary blood is obtained from a finger prick by the patient himself, and the blood drop obtained is deposited on filter paper, which can be stored at room temperature and then be sent to the laboratory by mail. 