Forabout25years researchanddevelopmentprojectsin thearea ofhuman-computer interaction (HCI) have been pursued with the objective to adapt the communication and interaction with the machine to the needs of the human user, and not vice versa. But it was only within the past ten years that signi?cant and substantial progress in the practical realization of the results in this area was achieved with the development of individual forms of interaction like speech processingor visualization.The resu- ing question, then, was whether it is possible to developeasy-to-use multimodaluser interfaces with an attractive market potential. This was the starting point for the inter-disciplinaryresearch activities in hum- computer interaction conducted by six large strategic cooperative projects with 102 partners from science and industry. In 1999, these six so-called lead projects came out ahead of 89 proposals overall in an ideas competition launched by the German federalgovernment.Theserecently?nishedresearchprojectsweresupposedtoallow human users in both their private and professional environments to multimodally control and diversely use technical systems via natural modalities of interaction like speech, gestures,facial expressions,tactile and graphicalinput.Ergonomicsanduser acceptance of these forms of interaction were the key criteria for the developmentof prototypes that were supposed to have both a strong scienti?c attractiveness and a high market potential.