For collaboration among users, sharing audio-visual, textual, graphical, or even interface-related information is the essence of computer-supported collaborative work (CSCW). Since most applications that are being used in private and work life these days are merely usable on the computer on which they are executed, collaboratively working with a single application is the most challenging part of CSCW. This is not only true because these applications are unaware that they are executed in a distributed environment, but, in particular, because of the numerous possibilities of data to be shared among the distributed users. Thus, the distribution of the application’s functionality over the network must be added transparently and, more important, subsequently without changing the application’s semantic. The effect has to be created at each remote site that the application is running locally and, therefore, can also be controlled by any remote user with a more or less immediate effect to the application. This problem is referred to as application sharing in the remainder of this article.