Contrast technique is applied for observing blood propagation in the cardiac cavity, enhancing the Doppler signal and examining myocardial perfusion. So far, bubbles have not been able to pass through the capillaries because of their relatively large size. Progress of bubble technology has made bubbles smaller than the diameter of the pulmonary capillaries, thus allowing transpulmonic left ventricular cavity opacification . These bubbles, however, will not opacify the myocardium well because of their dissolution during flow in the blood. Not air but gas bubbles such as fluorocarbon have been found to persist for a long time in the blood, resulting in obvious myocardial opacification. Moreover, new ultrasound technology using second harmonic images is used to make the myocardial opacification clear. Intravenous myocardial contrast echocardiography is a promising tool in a clinical setting. The combination of new contrast agents and new ultrasound technology makes it possible to demonstrate perfusion images of peripheral organs such as the liver, kidney and uterus.