Magnetic resonance (MR) examinations are used with increasing frequency to augment and replace other imaging modalities when a cardiovascular abnormality or thrombosis is suspected clinically. Because the signal intensity of flowing blood can vary greatly and can suggest the diagnosis of an intravascular mass, different pulse sequences and other imaging strategies may be needed to differentiate between flowing blood and intravascular thrombus. Some techniques image flowing blood as a signal void (black blood), whereas other methods enhance its signal intensity (white blood). Phase reconstruction, MR cine angiography, and related techniques that are sensitive to flow are assuming more importance in clinical MR diagnosis and are now replacing cardiac and thoracic angiography in selected clinical situations.