Personalized medicine aims to use individual biological signals to improve disease detection, risk stratification, and therapeutic selection. Such a strategy holds great appeal to practitioners, who are increasingly disillusioned with the “one size fits all” approach that characterizes contemporary medicine. Key to achieving these goals is integration of genetics and biomarkers with currently available clinical data. While the model of personalized medicine is appealing, many questions remain about which markers are diagnostic, prognostic, or pathologic.