This book constitutes the refereed proceedings of the 9th International Conference on Intelligent Tutoring Systems, ITS 2008, held in Montreal, Canada, in June 2008. The 63 revised full papers and 61 poster papers presented together with abstracts of 5 keynote talks were carefully reviewed and selected from 207 submissions. The papers are organized in topical sections on emotion and affect, tutor evaluation, student modeling, machine learning, authoring tools, tutor feedback and intervention, data mining, e-learning and Web-based ITS, natural language techniques and dialogue, narrative tutors...