Abstract: This invention provides biomarkers whose concentrations in blood plasma are associated with the presence or absence of PAD in the patient from whom the plasma sample is taken. The invention also provides biomarkers for distinguishing between PAD patients who are long claudicators and PAD patients who are not. In addition, the invention provides methods for identifying additional biomarkers, methods for detecting the biomarkers in patients, and methods for identifying agents, including pharmaceutical agents, which interact with the biomarkers and are useful for preventing or treating PAD in patients.