Why a book on contrast echocardiography? Over the past dozen years enough experience has accumulated to warrant a more extensive treatment of this method. Furthermore, there are new developments that suggest increased clinical utility for contrast echocardiography in the future. This book aims to summarize the "state of the art" for those interested in echocardiography - presumably mainly cardiologists, but here and there those of a more technical bent will find useful information as well. We feel that a more basic understanding of microbubble dynamics is necessary to advance research for such applications as transmission through the lungs, videodensitometric quantitation of cardiac output, intracardiac shunts, etc. All of these topics are extensively dealt with. The reader will note that many of the clinical chapters are written by pediatric cardiologists. This is only natural, since shunt detection and analysis of flow relationships are relatively more important in congenital heart diseases, and cur­ rently represent the most important uses for contrast echo cardiography in day-to­ day practice.