It has been proposed that acute eosinophilic pneumonia (AEP), which is characterized by the absence of recurrence, is associated with cigarette smoking (CS), because Japanese patients with AEP are young and have a high incidence of short-term smoking history. However, there has been no direct evidence that CS causes AEP. We hypothesized that tolerance might develop against repeated resumption of smoking cigarettes in CS-induced AEP cases. In this connection, we challenged a patient with CS-induced AEP with repeated resumption of CS, and it was demonstrated that CS induced AEP in conjunction with tolerance to repeated resumption of smoking.