慢性阻塞性肺病已是國內造成嚴重呼吸急症及死亡的廣泛疾病。證據顯示，約三分之一的穩定慢性阻塞性肺病主要是由嗜酸性球引起發炎反應而造成氣道阻塞。雖然慢性阻塞性肺病在臨床治療上所需要的嗜酸性球閾值仍有爭議，但嗜酸性球數值依然保有可引導治療的指標潛在力。特別的是，嗜酸性球的數量可以用來評估病人接受吸入性類固醇的效果，尤其在預防急性發作上更具效力。另外，許多針對嗜酸性發炎反應的治療都已經應用在臨床上或於研究進行中，包括標靶IL-5、IL-5 接受器、IL-4 及IL-13 的單株抗體。本篇綜論的目標旨在探討嗜酸性球的生物特性，還有它在慢性阻塞性肺病中對於急性發作和穩定疾病的角色，以及它作為輔助治療決策的臨床應用。

Chronic obstructive pulmonary disease (COPD) is a significant cause of domestic morbidity and mortality. Approximately a third of stable COPD patients have evidence of eosinophilic inflammation. Although the eosinophil threshold associated with clinical relevance in COPD patients is currently a subject to debate, eosinophil count holds potential as a biomarker to guide therapy. In particular, eosinophil count may be useful in assessing which patients may benefit from inhaled corticosteroid therapy, particularly regarding exacerbation prevention. In addition, several therapies targeting eosinophilic inflammation are available or in development, including monoclonal antibodies targeting the IL-5 ligand, the IL-5 receptor, IL-4, and IL-13. The goal of this review is to describe the biologic characteristics of eosinophils, their role in COPD during exacerbations and stable disease, and their use as biomarkers to aid treatment decisions.