All analyses will be conducted according to the intention-to-treat principle. Continuous data will be analyzed by t-test, categorical data by a chi-square test or Fisher's exact test when appropriate. The analysis of the creatinine trajectories stratified by treatment (and eventually by baseline GFR and T-cell-mediated rejection) will be performed by a mixed linear model with time and therapy as the independent parameters. The most applicable covariance matrices will be determined by graphical analysis and evaluated by the log likely hood ratio.