The long term objective is to develop reliable mens of noninvasively measuring blood flow. Disorders of the cardiovascular system are a major source of death and disability, including stroke, myocardial infarction and peripheral vascular disease. Many other diseases also secondarily affect blood flow. In this project two techniques of measuring blood flow in large vessels with NMR imaging will be developed and validated. An NMR imaging system designed for small animal work will be programmed to implement two different blood flow measurement imaging techniques. One uses the principle of washout of selectively saturated nuclei with a series of images made at different washout times to find the velocity through an imaged slice of known thickness. The other uses the phase shift (relative to stationary nuclei) acquired by nuclei moving along magnetic field gradients to find the velocity from the difference in phase between images made with an without flow-encoding magnetic field gradient pulses. Validation of the results of these two techniques will be performed using both controlled flows in an artificial flow system and independent measurement of flow in the cat carotid with an implanted ultrasonic flow meter. The use of surface coil detection of the NMR signal and EKG gating of the imaging process will be investigated in order to improve the reliability of the results. Extension of these techniques to the measurement of full three-dimensional flow velocities will also be investigated.