In the near future, robots used by people like personal computers will appear in office or at home. In this paper, we call these robots personal robots. A personal robot can be thought as a small autonomous mobile robot. First, we discuss a user interface design for personal robots in the face-to-face situation. Second, we consider features of personal robots and their environments, and propose a new user interface concept for a personal robot: Active Interface. To show the effectiveness of Active Interface, we design and implement a speech dialogue system called Chaser for human-robot interaction based on Active Interface.