Abstract: A method of measuring tissue perfusion in a human or non-human animal subject which comprises administering an effective amount of an ultrasound contrast agent to said subject, irradiating tissue in a target region with at least one pulse of ultrasound having energy sufficient to destroy or discernibly modify the echogenic properties of substantially all contrast agent in said target region, and ultrasonically detecting and quantifying the rate of flow of either further contrast agent into said target region or modified contrast agent out of said target region.