Many interactive systems, from virtual companions to online retailing, rely on socially interactive agents. These agents need to reach a good level of communication skills to conduct a conversation with humans and be acceptable and trustworthy by humans. This course will introduce non-verbal behavior generation models, present models for multimodal dialog, opinion detection, and voice quality, explain how to model the agent's emotions and their evolution over time, and present methods for enhancing naturalism with expressive gaze and gestures, etc.