Recent data show that monitoring cyclosporine A (CsA) concentrations with 2-hour postdose levels (C2) correlates with the incidence of rejection and graft outcome in de novo renal transplant patients. The purpose of the present work was to evaluate the advantage of C2 monitoring after the first year of kidney transplantation. We studied 161 patients, 96 on CsA-prednisone and 65 on triple therapy (Aza or MMF) who had been transplanted for a mean of 103+/-44 months. Mean serum creatinine (SCr) was 1.65+/-0.69 mg/dL, mean C0 was 174+/-44, and C2 was 667+/-194 ng/mL. Patients were classified according to C2 values:850 (n=29), between 850 and 450 (n=109), and450 (n=23) ng/mL. Patients with C2450 ng/mL displayed higher SCr values (1.97+/-0.99; 1.59+/-0.51; 1.52+/-0.4 mg/dL; P.001), received lower CsA doses (172+/-54; 207+/-54; 227+/-56 mg/d, P.01), showed lower C0 levels (155+/-48; 172+/-41; 199+/-45 ng/mL; P.001), and included more patients on triple therapy (54.5%; 44%; 17.2%; P.05). We found weak correlations between C0 and C2 (r=0.37), between C2 and CsA dose (r=0.36), and between C0 and SCr (r=-0.37). Among 117 patients followed up for 1 year with several C0 and C2 measurements, the coefficient of variation of C0 was 17% and of C2 was 21%. Graft functional deterioration occurred in 16 patients independent of the differences among the C2 groups, but 7 recipients (43.7%) had C0150 ng/mL and C2/C05. We conclude that C2 in monitoring stable patients needs further evaluation.