A method of using cavitate- or clathrate-forming host/guest complexes for the preparation of contrast media in ultrasonic examination is provided. The host/guest complexes have a host which dissolves in a liquid carrier, releasing the guest (inert gas). With such contrast media, it is possible to diagnose blood and its flow conditions in the heart, and other organs, such as the myocardium, liver, spleen, and kidneys. Other internal systems such as the urinary ducts, the gastrointestinal tract, joints, and eyes can also be imaged.