Diltiazem is a dihydropyridinic calcium-antagonist which acts an arterial muscle, producing an increase in vascular capacity. We administered it intraoperatively in 2 patients subjected to kidney transplantation, to asses the maximal vascular reserve of the transplanted organ. After 2' and 10' from administration of Diltiazem, Color Doppler Ultrasound showed a 30% increase in mean flow in the renal artery and 13% reduction in the intraparenchymal resistance rates with respect to the basal parameters. Systemic arterious pressure remained unchanged. This result was associated with an improvement in the perfusion of the transplanted organ.