Immunosuppressive medicines are characterized by specific pharmacokinetic profile which requires therapy monitoring by means of measuring their blood concentrations. Therapy monitoring, by means of determining blood concentration of the medicine, enables application of an optimal individual immunosuppressive therapy. Due to its variable pharmacokinetics, and small therapeutic index and potential interaction with numerous other medicines, the post-operative monitoring of immunosuppressive medicines is an essential element of therapy protocol for renal transplantation patients. Therapy monitoring represents an efficient way to reduce adverse effects of immunosuppressive medicines and to prevent transplantation rejection, by means of adapting the doses in renal transplantation patients. Determining the concentration of immunosuppressive medicines is of special importance in the modified dosing for patients with renal insufficiency. Pharmacokinetic analysis is important for proper interpretation of immunosuppressive medicines' blood concentrations. The interpretation of the received results must be multidisciplinary, considering that there are numerous factors of variability of patients and immunosuppressive medicines