We report cases of two patients with acute generalized exanthematous pustulosis(AGEP). One patient had localized cutaneous infection and the other rhinoplasty. Both were being treated with ampicillin and developed intense erythemas followed by generalized subcorneal pustulation associated with fever and a neutrophilic leukocytosis. Histopathological findings were subcorneal spongiform pustules showing preponderance of polymorphonuclear leukocytes. Generalized pustular psoriasis, subcorneal pustular dermatosis, impetigo and pemphigus foliaceus should be differentiated from AGEP. The causative drug in both of our cases was ampicillin and fast resolution of pustules was observed with a low dosage of systemic steroid within 5 days. (Korean J Dermatol 1998;36(2): 355-359)