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Recent technological progress made the creation of a humanoid interface to computer systems possible. An embodied conversational agent (ECA) is a computer-generated animated character that is able to carry on natural, human-like communication with users. For this purpose agent systems have been developed to simulate verbal and nonverbal communicative behaviours. ECAs can dialog with users using synthesised speech, gestures, gaze and facial expressions. In this Chapter we present our embodied conversational agent called Greta and focus on its capabilities of generating emotional expressive behaviours. Our 3D agent is able to communicate using the verbal and nonverbal channels like gaze, head and torso movements, facial expressions, and gestures. It follows the SAIBA framework that defines functionalities and communication protocols for ECA systems. The system generates the output animation in MPEG-4 standard. Our system is optimised to be used in interactive applications. It has a rich repertoire of expressive emotional behaviours. Several studies demonstrate that the application of facial expressions in embodied agents is justified. The agents that use emotional displays are perceived as mor