Two concepts of microbubble stabilization led to reproducible, industrially manufactured contrast agents, and to the transpulmonary stability of agents after intravenous injection. The albumin microencapsulation concept is represented by Albunex (Molecular Biosystems, San Diego, CA), the saccharide microparticle concept is represented by SH U 454 (Echovist and its transpulmonary derivative SH U 508 A, Schering AG, Berlin, FRG). In the past year, the first reported clinical studies of the transpulmonary agents have demonstrated their safety and efficacy. Further, the results of contrast-enhanced pulsed wave and color Doppler studies bring prospects of further improvements in vascular Doppler examinations. The patency of fallopian tubes was assessed with transvaginal scanning and transcervical injection of echogenic contrast agents. The feasibility of sonographic perfusion imaging of different organs (eg, myocardium, liver, tumors) was demonstrated using invasive injection techniques. Thus, ultrasound contrast agents are a new diagnostic tool in sonography and have a broad spectrum of potential indications.