The angiographic appearance of arterio-venous shunting has been reported in one previous case of a patient with acute severe transplant rejection. Two additional cases are presented here. In the first the arteriovenous shunting is massive, and the venous filling is within the first second of the study. In the second the shunting is less severe, and the venous filling occurs later in the arterial phase. Shunting is probably caused by multiple microscopic arterio-venous fistulae secondary to the vasculitis of rejection. We propose that the presence of arterio-venous shunting suggests renal transplant rejection and may indicate a poor prognosis for reversal of this rejection.