A 52-year-old woman, without a history of psoriasis, developed a widespread, sterile pustular eruption on the trunk and extremities 2 days after subcutaneous injection of dexamethasone solution. Skin biopsy revealed subcorneal pustules filled with neutrophils and moderate lymphohistiocytic infiltrate with a few eosinophils in the dermis. There was no evidence of vasculitis. Patch testing showed positive pustular reactions to dexamethasone solution. Histology of this pustule also resembled that of the original eruption. To our knowledge, acute generalized exanthematous pustulosis due to corticosteroid has not been previously reported.