An intact and patent renal vascular system is a prerequisite for even and complete perfusion during machine preservation and the reestablishment of renal blood flow after transplantation. Most of the so called "viability tests" for machine perfused kidneys refer to the cellular viability, not taking into account possible lesions of the vascular system. Angiography during machine preservation is a simple, safe and reliable means of examining alterations of the renal vascular system and detecting occult vascular pathology. The degree and reversibility of vasoconstriction can easily be demonstrated, as well as normal and pathologic perfusion patterns. Angiographic examination during preservation may be useful in addition to the tests of cellular viability in order to evaluate borderline kidneys prior to transplantation.