We present a trial consisting of 52 kidney transplant patients with stable function, following a transplantation period of 3-6 months (group1), 6-12 months (group2) and more than 12 months (group3) and monitored by CO, C2 and Cyclosporine levels in blood. Mean serum creatinine level were in 1.1, 1.3 and 1.4 Mg/dl for group 1, 2 and 3 respectively. Mean Neoral doses (mg/kg/day) were 5.5, 4.4 and 3.0 for each group respectively. Mean CO (ng/ml) was 347.6 (group 1), 265.6 (group 2) and 207.6 (group 3), and mean C2 was 1353.5, 1098 and 904.2 for each group. 40% (2/5patients) from group2 and 41% (17/41patients) for group 3, had overexposure of the graft to Neoral; meantime 24% (10/41 patients) from group 3 shown C2 levels of underexposure. We conclude CO is a poor predictor of graft exposition to cyclosporine and C2 reflect more exactly this exposure.