Focusing on the vision-based and sensor-based recognition and analysis of human activity and behavior, this book gathers extended versions of selected papers presented at the International Conference on Activity and Behavior Computing (ABC 2020), held in Kitakyushu, Japan on August 26 - 29, 2020. The respective chapters cover action recognition, action understanding, gait analysis, gesture recognition, behavior analysis, emotion and affective computing, and related areas. The book addresses various challenges and aspects of human activity recognition in both the sensor-based and vision-based domains, making it a unique guide to the field.