Fluorocarbon gases have been key to the recent development of several commercial injectable microbubble products that serve as contrast agents for ultrasound imaging. Microbubble-specific imaging is obtained by using harmonic and pulse inversion techniques. Controlled bubble destruction and monitoring of their re-entry into tissues provide unique tools for blood flow and tissue perfusion studies. Contrast echosonography allows assessment of structural and functional cardiovascular abnormalities and solid organ lesions, including tumors. New microbubble agents that target specific tissues, allowing molecular imaging of thrombi, atherosclerotic plaques, inflammation area and angiogenesis related to tumor growth, are being investigated. Microbubbles also have potential as therapeutic tools, and as targeted and ultrasound-triggered drug and gene delivery systems. (C) 2003 Elsevier Ltd. All rights reserved.