Background: Acute generalized exanthematous pustulosis (AGEP) is a rare and severe subtype of drug eruption, characterized by acute, extensive, non-follicular, sterile pustules on an erythematous background, accompanied by fever and leukocytosis. Objective: The purpose of this study was to characterize AGEP in Korean patients in terms of clinical, laboratory, and pathologic findings. Methods: Thirty-six patients (M:F=17:19) with AGEP were identified from an extensive review of medical records over a 15 year period. All patient cases were confirmed by biopsy and fulfilled the diagnostic criteria. Results: The patient ages ranged from 4∼80 years (37.6±19.4). The incubation period was 1∼23 days. The duration of disease was 5∼14 days. Neutrophilia (36/36), high CRP (14/36), and eosinophilia (30/36) were common laboratory findings. A history of drug administration existed in 23 of 36 patients; herbal medications, lacquers and radiocontrast media were the unique causative drugs. Spongioform subcorneal or intraepidermal pustules in the epidermis was observed in all patients. Thirty-six patients were subdivided into 2 groups: group A (n=23) was strongly associated with known agents; and group B (n=13) had no identified causative agents. There was no significant difference between the 2 groups. Conclusion: Our results demonstrate the characteristic features of AGEP in Korean patients as follows: lower identification of causative agents; herbal medications, lacquers, and radiocontrast media were the main causative agents; and no significant differences existed between the 2 groups. (Ann Dermatol 22(2) 163∼169, 2010)