Ultrasound at frequency 1 MHz can accelerate thrombolysis in an in vitro system using streptokinase, urokinase, or t-PA. [C. W. Francis et al., J. Clin. Invest. 90 2063--2068 (1992)]. Ultrasound can also hasten reperfusion due to thrombolytic agents both in vitro [D. Harpaz et al., Am. Heart J. 127, 1211--1219 (1994)] and in vivo [R. Kornowski et al., Circulation 89, 339--344 (1994)]. The mechanism is nonthermal, probably related to cavitation. This type of thrombolysis which is associated with relative low intensity, high-frequency ultrasound is to be distinguished from the high intensity, low-frequency (~ 20 kHz) ultrasound that has been proposed for ``ultrasound angioplasty'' [A. Ernst et al., Am. J. Cardiol. 73, 126--132 (1994)]. Potential clinical applications and problems and limitations to the clinical application of ultrasound accelerated thrombolysis and ultrasound angioplasty will be discussed. An ``acoustic filter'' has been developed with the goal of removing microbubbles from cardiopulmonary bypass equipment, preventing neurologic damage [K. Q. Schwarz et al., J. Thorac. Cardiovasc. Surg. 104, 1647--1653 (1992); US Patent No. 5,334,136, 2 August 1994].