The role of new and emerging biomarkers in risk prediction has become a topic of significant interest and controversy in recent times. Currently, available models for risk prediction are reasonably good yet still misclassify a not insignificant portion of the population. The sheer number of new potential risk markers is daunting, and it is difficult to assess the importance of each one over and above the traditional risk factors. Endothelial function is one potential biomarker of risk that has been extensively studied. However, while it has demonstrated some utility in risk prediction, its use in daily clinical practice is yet to be clearly defined. The present review assesses the prognostic significance Of measures of endothelial function.