When writing programs for interactive computer systems, programmers often find that it is difficult to develop the interactive dialog these programs require. The difficulty arises for two reasons. First, because interactive terminals are relatively new, programmers are not accustomed to planning and developing computer dialogs. Second, there is often no easy way to program the dialog once it has been developed. The solution to the first problem is heavily dependent on the programmer, his training and his background, and does not lend itself to a computerized solution. The solution to the second problem, however, can be eased by providing a higher-level, dialog construction language. The basic features for such a language appear in several systems used for computer-aided instruction [1--4]. The Message System builds on these features to provide a dialog construction language for general use.