Summary:A 52-year-old man developed a severe anaphylactic reaction after a wasp sting. Slurred speech and left hemiparesis were noted a few hours later. Three-and-one-half weeks later, he became acutely obtunded and quadriparetic. Angiographic studies demonstrated complete and near-complete occlusions of the right and left internal carotid arteries, respectively. A mechanism is suggested for delayed ischemic stroke after wasp sting anaphylaxis that involves cerebrovascular sympathetic innervation.