Among 105 patients given recombinant tissue plasminogen activator (rt-PA, alteplase) intravenously for acute stroke, 2 (1.9%) had lingual angioedema, which progressed to a fatal anaphylactoid reaction in 1. The authors review the 2 cases and possible mechanisms responsible. They warn that patients who are taking an angiotensin-converting-enzyme inhibitor may be at increased risk for angioedema with concomitant alteplase therapy.