The endothelial glycocalyx can be described as a network of membrane-bound proteoglycans and glycoproteins, covering the luminal surface of endothelial cells. Over the past decades, structural properties and functions of glycocalyx have been increasingly examined, underlining its role in many physiological processes. This article provides the basis on composition and functions of the endothelial glycocalyx. The Author also describes the so called “endothelial dysfunction” and how it can lead to the development of pathological inflammatory processes and consequent vascular diseases.