specialists contribute their own assessment of specific aspects of MC- 20E and illustrate the method's principles as well as applications. We were faced with inevitable overlaps and some repetitions in the discussion of quan­ titative potentials or limilations of the methodology. Rather than strictly 'streamlining ' the text, we decided to accept some redundancy in the interest of presenting a diversity of points of views, reflecting the current evolutionary state of MC-20E. Following a brief reference to the established clinical contrast echocardiog­ raphy, recent developments and validations of the specialized MC-2DE tech­ nique are reviewed, bearing in mind that the field is in a flux and some of the ongoing activities have not as yet been formally reported. Mechanisms of the echo contrast and several new agents are decribed next, and an additional chapter illustrates current thoughts-on optimizing the echo contrast medium.