Investigation of blood flow in the heart and vessels may provide insight into the function of the cardiovascular system and aid patient management decisions. Phase velocity cine magnetic resonance imaging (PVC MRI) is a powerful and accurate noninvasive technique to quantitate and analyze blood flow. This article describes the principles, performance, and potential limitations of PVC MRI measurements. Clinical applications of PVC MRI are then reviewed with an emphasis on the assessment of congenital heart disease.