Cyclosporine absorption has been key to obtaining adequate results in immunosuppressive regimens. Since 2005, we have used a different monitoring program for Cyclosporine among pediatric liver transplant recipients namely, two hours post dosing concentrations (O(2)). This study of 128 patients included 50.8% males and 64.8% recipients of cadaveric livers. Their main reasons for transplantation were as follows: 43.8% acute liver failure and 37.5% biliary atresia. Mean age at time of transplantation was 5.4 +/- 4.5 years for boys and 3.4 +/- 3.3 years for girls. Mean age at the beginning of C(2) monitoring was 8.9 +/- 4.8 years and time elapsed since transplantation was 53.6 +/- 36.4 months. The initial Cyclosporine dose of 5.5 +/- 5 mg/kg/d had been reduced by month 24 to 4.5 +/- 1.5 mg/kg/d. Estimation of glomerular filtration rate (eGFR) was performed using the Schwartz formula. Baseline creatinine and eGFR were 0.73 +/- 0.49 mg/dL and 111.99 +/- 28.27 mL/min.m(2) versus 24-month creatinine and eGFR of 0.69 +/- 0.20 mg/dL and 122.26 +/- 24.47 mL/min.m(2), respectively (P < .05). Eight patients experienced acute rejection episodes, 4 had chronic rejection, 3 posttransplantation proliferative diseases (PTLD) were reported, and 2 patients died. Cyclosporine C2 monitoring allowed a trend toward long-term dose reduction. Consequently we observed significant improvement in renal function. Acute/chronic rejection rates were low, which suggested that C(2) monitoring was effective to control immunosuppressive therapy.The low incidence of PTLD and patient mortality showed that there was an adequate balance between safety and efficacy profiles.