A very important aspect in developing robots capable of human-robot interaction (HRI) is natural, human-like communication. Besides a flexible dialog system and speech understanding an anthropomorphic appearance has many advantages for intuitive usage and understanding of a robot. As a consequence of our effort in creating an anthropomorphic appearance and to come as close as possible to a human-human interaction, we decided to use human-like sensors, i.e., two cameras and two microphones only, not using a laser range finder or omnidirectional camera for tracking persons. Despite the challenge of a limited field of perception, a robust attention system for tracking and interacting with multiple persons simultaneously in real-time was created. Our approach is sufficiently generic to work on robots with varying hardware, as long as stereo audio data and images of a video camera are available. Since the architecture is designed modular with a XML based data exchange we are able to extend the robot's abilities easily