The aim of this study was to estimate the incidence of anaphylaxis in an emergency department, identify rate and risk factors of recurrent anaphylaxis, and describe its clinical features and management. A retrospective study of patients who attended the emergency department at Thammasat University Hospital was conducted during 2003-2004 with anaphylactically related ICD-9 and ICD-10 terms. There were 64 patients who experienced 65 anaphylactic episodes during the 1-year period. The anaphylaxis occurrence rate was 223 per 100,000 patients per year. The most common manifestations were cutaneous symptoms and signs, followed by respiratory expression. Food allergy was the most common cause of anaphylaxis. Eighty-five percent of admitted cases had monophasic anaphylaxis. Patients with and without biphasic reactions did not differ significantly in terms of epinephrine and steroid usage. In conclusion, anaphylaxis is not rare. Epinephrine and steroid usage did not prevent biphasic reactions.