The development of large-scale dialog systems requires a flexible architecture model and adequate software support to cope with the challenge of system integration. This contributionOur current work in the context of the SmartKom project has been funded by the German Federal Ministry for Education and Research (BMBF) under grant 01 IL 905 K7. presents a general framework for building integrated natural-language and multimodal dialog systems. Our approach relies on a distributed component model that enables flexible re-use and extension of existing software modules and is able to deal with a heterogeneous software environment. A practical result of our research is the development of a sophisticated integration platform, called MULTIPLATFORM, which is based on the proposed framework. This MULTIPLATFORM testbed has been used in various large and mid-size research projects to develop integrated system prototypes.