Abstract: Effective Command and Control Systems depend upon timely and consistent information exchange between headquarters and operational units. Information can be sent and received by a wide range of systems and in an ideal world everyone would have the same system, the same database, the same operating system, the same computing platform, and so on - thus making information exchange much easier to achieve. However, that is not the case and it would be only the most optimistic amongst us who would acknowledge that this could ever be achieved, particularly in allied and combined operations. This short paper introduces the concept of interoperability using message text formats (MTF) as defined by the NATO standard ADatP-3 (Allied Data Publications number 3), Australian ADFORM (Australian Defence Formatted Message) or USMTF (United States Message Text Formats). In order to do this it is necessary to explain what is meant by interoperability in terms of unambiguous information exchange. As an example, from time to time, use is made of the Systematic COTS product IRIS. IRIS has been accepted by NATO as a product capable of preparing and validating ADatP-3 messages and, in the USA, has been approved for inclusion in the DII-COE (Defence Information Infrastructure - Common Operating Environment) as well as being approved for USMTF 97, 98 and 99. By using modern software products like IRIS, the problem of interoperability can be resolved using formatted messages.