Cyclosporine A (CyA), tacrolimus (FK 506), and mycophenolic acid are routinely utilised immunosuppressive drugs used in the prevention of allograft rejection and the treatment of several autoimmune diseases. The monitoring of CyA blood levels plays the most important role to individualize the dosage regiment and to minimize acute rejection risk and drug toxicity. Inadequate low CyA doses and levels may result in the rejection of transplanted organs. Toxic levels of CyA are associated with many serious side effects, including nephrotoxicity, hepatotoxicity, and a range of other complications. In the period of 1999-2002, 12,859 analyses of whole blood CyA levels were performed at our Department of Clinical Biochemistry. The aim of the present paper is to establish a new monitoring strategy of CyA that consists in the use of a single sampling point at 2 hours postdose and the estimation of blood concentration (C2). For the transplant patient, C2 monitoring is a significantly much better predictor of drug exposition and pharmacokinetic estimation than the trough concentration monitoring before the next dose (C0) used until now. The C2 monitoring strategy reduces the incidence and severity of both acute organ rejection and cyclosporine A toxicity.