After clinical evaluation, especially clinical prediction rules, appropriately ordered venous duplex has become the standard test for evaluating and excluding deep vein thrombosis (DVT). Ultrasound is useful for lower- and upper-extremity veins. Protocols include grayscale, color Doppler, and spectral Doppler. Recommended lower-extremity protocols include central leg and calf veins. Duplex Doppler is widely used to evaluate patients with chronic venous disease, especially with suspected venous reflux. Mapping to identify adequate veins before surgery is another widely used indication for venous ultrasound. Ultrasound for thrombosis can be characterized as normal, acute DVT, superficial thrombosis, or chronic postthrombotic changes in most patients.