This paper reports on the creation of the multimodal NIMITEK corpus of affected behavior in human-machine interaction and its role in the development of the NIMITEK prototype system. The NIMITEK prototype system is a spoken dialogue system for supporting users while they solve problems in a graphics system. The central feature of the system is adaptive dialogue management. The system dynamically defines a dialogue strategy according to the current state of the interaction (including also the emotional state of the user). Particular emphasis is devoted to the level of naturalness of interaction. We discuss that a higher level of naturalness can be achieved by combining a habitable natural language interface and an appropriate dialogue strategy. The role of the NIMITEK multimodal corpus in achieving these requirements is twofold: (1) in developing the model of attentional state on the level of user’s commands that facilitates processing of flexibly formulated commands, and (2) in defining the dialogue strategy that takes the emotional state of the user into account. Finally, we sketch the implemented prototype system and describe the incorporated dialogue management module. Whereas the prototype system itself is task-specific, the described underlying concepts are intended to be task-independent.