The endothelium was originally thought to be just a semipermeable barrier between the vessel wall and the bloodstream, but today we now realize that it is actually a highly active autocrine, paracrine, and endocrine organ. Researchers have also begun to realize that the endothelium plays a key role in the development of atherosclerosis as well as other diseases. This increased recognition has resulted in considerable effort by both researchers and clinicians to develop accurate and reliable methods to measure and track changes in both vascular structure and function. In addition, research interest has focused on various cardiovascular risk factors (eg, age, gender, obesity, physical inactivity) and the effect they have on vascular structure and function. In this review, the authors discuss different research and clinical methods to assess vascular structure and function as well as the effect of various cardiovascular risk factors on the endothelium and the vascular system. They also discuss the ability to modify vascular structure and function through various lifestyle modifications such as weight loss and exercise. © 2010, SAGE Publications. All rights reserved.