This book constitutes the refereed proceedings of the first International Conference on Adaptive Hypermedia and Adaptive Web-Based Systems, AH 2000, held in Trento, Italy, in August 2000. The 22 revised full papers presented together with 35 short papers were carefully reviewed and selected from 55 submissions. Among the topics covered are hypertext, user modeling, machine learning, natural language generation, information retrieval, intelligent tutoring systems, cognitive science, web-based education, etc.