The Journal of Multimodal User Interfaces stands at the crossroads between computer science, behavioral sciences, signal processing and several other related disciplines such as graphic and industrial design, linguistics, social sciences, cognitive psychology, electronic engineering and human engineering. This second issue of JMUI under the aegis of Springer accommodates selected research papers which have come out of a major research effort within FP6 European project SIMILAR: “Human-machine interfaces similar to human-human communication” under the leadership of Benoit Macq. Notably, the sequence of workshops, called eNTERFACE, funded by the SIMILAR project has created a prolific medium of interaction and cooperation between major laboratories and universities. The five papers in this issue are in fact an outcome of four years of cooperative work within the framework of these workshops. The first three papers involve human-machine interaction in technologically endowed environments. For example the paper entitled “Multimodal Identification and Localization of Users in a Smart Environment” addresses the problem of localization and identification of users in equipped rooms. The system makes use of motion detection, person tracking, face identification, feature-based identification, audio-based localization, and audio-based identification modules, and fusing all this information with particle