This book constitutes the refereed proceedings of the 5th InternationalWorkshop on Intelligent Virtual Agents, IVA 2005, held in Kos Island, Greece in September 2005. The 26 revised full papers and 14 revised short papers presentedtogether with the abstracts of 15 poster papers were carefully reviewedand selected from 69 submissions. The papers are organized in topicalsections on IVAs and education, conversational agents/NLP, IVAarchitectures, cognition, reasoning and behaviour, nonverbalcommunication, storytelling/interactive narrative, social intelligence, emotions/affect/personality, evaluation and methodology, and the postersession.