It is well known that microbubble destruction can occur during contrast echocardiography, primarily by acoustic cavitation (1). The propensity of microbubbles to undergo this process when exposed to ultrasound depends on physical properties of both the bubbles themselves and the ultrasound beam. Higher rarefactional peak amplitude (a measure of ultrasonic acoustic power) and lower frequencies cause greater microbubble destruction (1–3). Thickness, compressibility, and elasticity of the microbubble shell are important factors in their susceptibility to ultrasoundmediated destruction (4). The ability to destroy microbubbles has useful clinical applications, allowing the quantification of myocardial perfusion using replenishment curves (5). Also, we and others (6) have begun to investigate this attribute of microbubbles as a method for targeting gene or drug delivery.