Cyclosporine is extensively metabolized in liver, mainly through cyp3A4 enzyme system. There are more than 30 identified cyclosporine metabolites. It’s major metabolite is M17 that has about 10% immunosuppressive activity. Because of the small therapeutic spectrum, the differences in absorption and metabolism, wide differences in kinetic between and within patients, determination of CyA and M17 concentration for dosage adjustment in kidney transplant recipients is necessary. In this study we developed a simple, specific HPLC method which is easy to use and available in most of clinical centers to adjust the dosage. 13 kidney transplant candidates (4 female and 9 male, age 20-65 years, first time transplant) were selected. The pharmacokinetic parameters were determined following single dose administration of CyA, 12 hours before transplantation and also at trough level in the steady state condition after transplantation for both CyA and M17. We found that: 1) M17 concentration was higher in females, probably due to the effect of progesterone on the activity of cyp3A4. 2) Clearance was lower in patients>40 years old, may be because of high lipoprotein level in older ages. 3) A saturable metabolism relative to AUC in sampling intervals was found in most patients having higher weight. 4) Different pharmacokinetic parameters obtained in patient with same body weight, show that drug administration considering body weight is not rational. According to the good correlation found between CyA and M17 concentration at 8, 10, 12 hours with those of AUC following single dose of CyA, these parameters can be used as an index in dose adjustment individually, also from above parameters the K, t1/2 and AUC (M17/CyA) at times of 10 and 12 hours can be found.