Color Doppler is a special ultrasound technique which allows us to evaluate blood vessels. Using the Doppler principle, ultrasound waves reflect the red blood corpuscles in the arteries and veins and they are evaluated for velocity using amplitude and color maps of the vessels. Colour Doppler is very useful in evaluating the carotid arteries in the neck, the heart (echocardiography), the arteries and veins in the abdomen and the arteries and veins in the upper and lower limbs to detect clots in the bloodstream. This friendly, non-invasive procedure has remarkable accuracy so that physicians can immediately institute measure.