Video surveillance is currently undergoing a rapid growth. However, while thousands of cameras are being installed in public places all over the world, computer programs that could reliably detect and track people in order to analyze their behavior are not yet operational. In this context, this book presents a complete approach for automatically detecting and tracking an unknown number of interacting people from multiple cameras located at eye level. The proposed system works reliably in spite of significant occlusions and delivers metrically accurate trajectories for each tracked individual. Furthermore, the approach is extended with a method for representing the most common types of motion in a specific environment and learning them automatically from image data.