Exacerbations of COPD are episodes of worsening symptoms characterized by increased airway and systemic inflammation. If systemic inflammation is a cause of endothelial dysfunction in COPD, endothelial function would be suspected to be further impaired during exacerbation and recover thereafter. The purpose of this study is to determine a possible association between the clinical entity of exacerbation, markers of systemic inflammation and endothelial dysfunction in patients with COPD.