Emotion- and attention-related subjective and physiological responses to virtual proximity and facial expressions of embodied computer agents (ECA) were studied. Thirty participants viewed female and male characters with a neutral, unpleasant, or pleasant facial expression. Agents' size was used to simulate three levels of proximity. Participants' electrical facial muscle and heart activity were registered, and subjective ratings of emotional and attentional experiences collected. Unpleasant and large (i.e., closer) agents were more alerting (i.e., unpleasant, arousing, and dominating) and attracted more stimulus-driven attention than neutral, pleasant, and smaller (i.e., further away) agents. Pleasant agents attracted more voluntary attention than neutral and unpleasant agents. Heart rate (HR) responded to agent proximity, while the valence of the agent affected electrical facial muscle activity. Thus, the imitation of human social emotional cues in embodied computer agents (ECAs) could be used to regulate human–computer interaction. Copyright © 2010 John Wiley & Sons, Ltd.