Cyclosporin A (CsA) is an immunosuppresent with a narrow therapeutic window. Inter and Intra patient variability necessitates frequent blood level monitoring in transplant patients. The purpose of the present study was to evaluate CsA blood concentrations in order to find out the best time for sampling in Iranian children with kidney transplant. CsA levels were determined using a radioimmunoassay (RIA) in 29 (16 boys and 13 girls) pediatric transplant recipients with stable renal function. Mean age was 14.5 ± 2.3 years. The mean CsA dose was 4.7 ± 0.4 mg/kg/day. There was a high correlation between CsA dose, serum creatinine and C1.5 level. There was no correlation between C0 and above mentioned parameters. In conclusion, for using single point monitoring, C1.5 CsA levels seems more accurate than C0 in Iranian pediatric transplantation patients.