Novel biomarkers have the great potential to dramatically change the decision making process of modern medicine. Recently there has been increased interest in the use diagnostic or prognostic markers for accurately diagnosing disease or predicting the risk of future clinical events. In this talk, we introduce various concepts of accuracy measures for quantifying the clinical utility of biomarkers under such settings. When new biomarkers are introduced to improve the diagnostic or prognostic accuracy of existing modalities, it is important to quantify the incremental value of new markers. We will also discuss various procedures for making inference about such incremental values. These methods will be introduced under various study designs.