This poster presents an overview of the work on an interaction manager of a platform for multimodal applications in 2.5G and 3G mobile phone networks and WLAN environments. The poster describes the requirements for the interaction manager (IM), its tasks and the resulting structure. We examine the W3C's definition of an interaction manager and compare it to our implementation, which accomplishes some additional tasks. Categories and Subject Descriptors H.5.2 [Information Interfaces and Presentation (e.g., HCI)]: User Interfaces ? Evaluation/methodology, User interface management systems (UIMS) General Terms Design, Experimentation, Human Factors, Languages. Keywords Multimodal interface, session management, interaction manager, device independence, multi-user applications, mobile network.