Abstract: A method for evaluating cyclosporine-related nephrotoxicity in a patient receiving cyclosporine therapy is disclosed. The method comprises measuring urine kallikrein content utilizing radioimmunoassay specific for human urine kallikrein. The value obtained is compared then to a pre-treatment value of urine kallikrein levels.Also disclosed is a means for predicting susceptibility to cyclosporine-related nephrotoxicity. Potential cyclosporine therapy patients are evaluated according to their baseline (pre-treatment) urinary kallikrein levels. Low initial levels of urine kallikrein are predictive of susceptibility to cyclosporine-related nephrotoxicity.Also disclosed is a method for monitoring cyclosporine-related nephrotoxicity during the course of cyclosporine treatment. Decreased urinary kallikrein indicates that cyclosporine administration should be decreased or terminated. Increased urinary kallikrein indicates that cyclosporine administration may be increased or maintained.