Hemodynamic instability may occur during liver transplantation especially following unclamping the portal vein. A period of hypotension (postreperfusion syndrome) is usually responsive to treatment with fluids, calcium, sodium bicarbonate, and vasoactive drugs, but if hypotension persists, other causes must be sought out. In this report, we present a case in which anaphylaxis, most likely due to a component of the University of Wisconsin preservation solution, occurred coincident with liver reperfusion and severely exacerbated reperfusion hemodynamic instability. To our knowledge, this is the first report of anaphylaxis at the time of reperfusion and may provide an explanation for cases of vasoplegic syndrome associated with graft reperfusion.