We have previously reported our experience on CsA lymphocyte (Lc) maximum level (LTmL) as a new alternative for CsA monitoring in stable kidney transplant patients. This study was conducted to determine the temporal variations of LTmL, Cmax (whole blood maximum CsA concentration), CsA dose and the Lc count in patients with De novo kidney transplant. CsA LTmL, Cmax and Lc count were prospectively measured in 37 patients at 1, 2 and 3 months post kidney transplantation. Patients were divided into 2 groups: rejection group (REJ) with biopsy-proven acute rejection and a normal group (NORM) with normal graft function. Both groups were compared according to CsA LTmL, Cmax, dose and Lc count. Acute Rejection (13.5%) occurred at 2 months in 2 patients and in 2 others at 3 months post transplant. Both groups had similar LTmL (100 ± 43 vs 102 ± 85 pg/Lc), Cmax (1439 ± 836 vs 1471 ± 796 ng/ml), Lc count (1637 ± 1100 vs 1638 ± 1143 /ml) and CsA dose (6.5 ± 0.6 vs 6.7 ± 1 mg/kg) at the first month. REJ patients had significantly lower LTmL at 2 and 3 months (59 ± 34 and 39 ± 1.5 pg/Lc) and higher Lc count (2045 ± 783 and 2032 ± 220 /ml) when compared to their NORM counterparts (87 ± 56 and 63 ± 30 pg/Lc) with p < 0.05 and (1375 ± 738 and 1561 ± 603 /ml) with p < 0.003 respectively. Unexpectedly Cmax was significantly higher in the REJ group (2045 ± 783 vs 1375 ± 738 ng/ml, p< 0.02) at 2 months and comparable to the NORM one at 3 months (11144 ± 340 vs 13654 ± 525 ng/ml, p = NS). These results suggest that acute rejection is associated with a relatively low CsA LTmL and high Lc count in the early post-transplant period. Surprisingly, CsA Cmax failed to correlate with clinical outcome. CsA LTmL seems to offer a more reliable alternative then Cmax for CsA monitoring in patients with kidney transplantation.