Acute generalized exanthematous pustulosis (AGEP) is a rare, drug-related pustular eruption usually starting from folds with edema and erythema and with subsequent spreading. Clinically AGEP is characterized by the sudden appearance of dozen of sterile, non follicular, small pustules on erythematous and edematous skin. Mild non erosive mucosal involvement, mostly oral, may sometimes occur. Fever, neutrophilia and peripheral blood eosinophilia (in a third of patients) are present. Other skin signs such as facial edema, purpura, target-like lesions and blisters have been described but are not typical for AGEP. Diagnostic criteria for AGEP were established by an international committee of experts, the European Study of Severe Cutaneous Adverse Reactions (EuroSCAR). The most relevant histopathological feature is represented by the detection of non-follicular subcorneal and/or intracorneal spongiform pustules that are usually large, contiguous and tend to coalesce. After elimination of the causative drug, pustules usually spontaneously disappear in a few days with desquamation and the reaction fully resolves within 15 days. Internal organs are not usually involved and no systemic treatment is required. Withdrawal of the culprit drug is mandatory. Although AGEP is a self-limiting disease with a favourable prognosis, secondary infections are a not infrequent complication in patients in poor general medical conditions. The reported mortality is about 5%. The most severe cases are associated with drug rechallenge.