To determine the rate of clinically significant recurrence of symptoms in patients treated for anaphylaxis in the ED. Retrospective chart review of out-of-hospital, ED, and hospital records over 4.5-year period (July 1991 to December 1995) at a university hospital ED with an annual patient volume of 60,000. Subjects were ED anaphylaxis patients with > or = 2 of the following 3 organ systems involved: cutaneous, respiratory, and cardiovascular. The major outcome criterion was recurrence of symptoms after ED release. Recurrences were sought at the primary treatment hospital and at surrounding hospitals (radius of 75 miles from the primary institution) within a 7-day period from the initial visit. Review of the state death registry also was made to verify the absence of out-of-hospital deaths. The medical records of 1,261 allergic reaction patients were reviewed, with 67 (5.3%) cases of anaphylaxis identified. Symptoms and signs in patients during the ED phase included: dyspnea, 42 (63%); pruritus, 38 (57%); emesis, 27 (41%); throat/chest tightness, 25 (37%); orthostatic complaints, 12 (18%); urticaria, 47 (70%); circulatory shock, 32 (48%); upper airway angioedema, 7 (33%); stridor, 11 (16%); and bronchospasm, 20 (30%). Of the 67 patients, 93% had immediate resolution and remained asymptomatic for a mean time of 4.2 hours in the ED. Protracted reaction occurred in 5 cases (3 using beta-adrenergic blocking agents). For 19 (28%) patients admitted to hospital, the mean hospital length of stay was 63 hours. Only 2 (3%) recurrent cases were identified, both manifested solely by urticaria. The authors conclude that recurrent anaphylactic reactions were rare, occurring in 3% of cases and without life threat in this patient population. Selective outpatient management of patients with severe anaphylactic reactions that promptly respond to therapy with complete, rapid resolution may be reasonable. Further study of this medical emergency is required to develop criteria to guide the choice of an outpatient disposition.