Idiopathic hypereosinophilic syndrome is characterized by multiorgan involvement without any cause, and peripheral eosinophilia(1,500/μl) for more than 6 months. Clinically, many organs can be involved, but the heart is the most commonly involved organ. Although lung involvement is usual(20-30%)1) in hypereosinophilic syndrome, there are few reports of eosinophilic pneumonia proven by biopsy confirmation in Korea. We experienced a case of hypereosinophilic syndrome with eosinophilic pneumonia and bron- chitis confirmed by biopsy, and we report it here with a review of the literature. (J Asthma Allergy Clin Immunol 21: 662-7, 2001)