This book presents a project that consists on the development of a receptionist robot for the Institute for Systems and Robotics (ISR), Lisbon. This robot is stationed at ISR's lobby, where it waits for nearby visitors. At this point it attempts to interact with them in order to find out whether they wish to be lead to a specific room on this floor. The followed development methodology focuses on the integration of several modules, featuring navigation and localization capabilities, a graphical interface, speech recognition and synthesis, people detection, face detection, and behavior control, in order to achieve an autonomous system. In order to save time and effort, as well as obtaining a robust solution, "off-the-shelf" software packages are used whenever possible. The present theses focuses, apart from the conception of the robot's hardware and software architecture design, on its human-robot interaction capabilities, as well as on the integration and coordination among all modules.