This book focuses on how interactive, multimodal technology such as virtual agents can be used in training and treatment (social skills training, cognitive behavioral therapy). People with socio-affective deficits have difficulties controlling their social behavior and also suffer from interpreting others' social behavior. Behavioral training, such as social skills training, is used in clinical settings. Patients are trained by a coach to experience social interaction and reduce social stress. In addition to behavioral training, cognitive behavioral therapy is also useful for understanding better and training social-affective interaction. All these methods are effective but expensive and difficult to access. This book describes how multimodal interactive technology can be used in healthcare for measuring and training social-affective interactions. Sensing technology analyzes users' behaviors and eye-gaze, and various machine learning methods can be used for prediction tasks. This bookfocuses on analyzing human behaviors and implementing training methods (e.g., by virtual agents, virtual reality, dialogue modeling, personalized feedback, and evaluations). Target populations include depression, schizophrenia, autism spectrum disorder, and a much larger group of social pathological phenomena.