Atherosclerosis is the leading cause of death in the Western world. In the lower limbs, this condition can manifest itself as peripheral arterial disease (PAD), with a clinical presentation ranging from asymptomatic disease to critical limb ischaemia. The presence of PAD indicates a severe degree of systemic atherosclerosis. Due to the generalised nature, diagnosis of the condition is concurrently a strong predictor of risk of cardiovascular morbidity and mortality. PAD can be diagnosed non-invasively by measuring the blood pressure at the ankle or toe level and calculating a ratio with the arm pressure. Reliable measurements are pivotal for both detection of the disease and selection of the optimal treatment. This book targets various methodological issues regarding the diagnostic accuracy of automated non-laboratory as well as laboratory methods including signal interpretation and diagnostic agreement.