This book contains 22 long papers and 13 short ones selected for the Scientific Track of the Third Congress of the Italian Association for Artificial Intelligence. The long papers report completed work whereas the short papers are mainly devoted to ongoing research. The papers report significant work carried out in the different subfields of artificial intelligence not only in Italy but also elsewhere: 8 of the papers come from outside Italy, with 2 from the United States and 1 eachfrom Australia, Austria, Germany, The Netherlands, Spain, and Turkey. The papers in the book are grouped into parts on: automated reasoning; cognitive models; connectionist models and subsymbolic approaches; knowledge representation and reasoning; languages, architectures and tools for AI; machine learning; natural language; planning and robotics; and reasoning about physical systems and artifacts.