The introduction of next generation communication systems will enable the provisioning of novel services and applications. Powerful multipurpose handheld terminals are already available for the mass-market and will be omnipresent in future communication scenarios. Although individual user interface technologies are improved continuously, new approaches how to realize user-friendly user interaction in such future systems are imperative. Distributed user interfaces enable the remote use of devices and services. Humans can control their environment, e.g. their home appliances, from any place with different kind of terminals. They are not longer restricted to the limited user interfaces provided by devices themselves. New communication paradigms demand for systems that adapt to the human instead of forcing him to submit to the given technical solutions, as it is usual today. Such demands and corresponding visions provide the requirements and necessities that have to be considered in future developments. The 'I-centric communications' research program develops an open architecture following these new communication paradigms and will realize prototype implementations. This paper introduces the vision of I-centric communications and its effects on user interfaces.