Activated eosinophils is a major cell type to be mainly involved in allergic diseases. Recent studies also indicated that eosinophils play an important role in the pathogenesis of chronic obstructive pulmonary disease (COPD), especially asthma-COPD overlap and/or eosinophil COPD. The aim of this study is to clarify cellular characters of human eosinophils in patients with asthma-COPD overlap and/or eosinophil COPD.