The Portuguese Association for Artificial Intelligence hasbeen organizing Portuguese Conferences on ArtificialIntelligence, now held every second year, since 1985.This volume contains selected papers from the FifthConference on Artificial Intelligence. The conference has aninternational status: 62 contributions from 13 countrieswere received, of which 26 were from Portugal. To guaranteea high scientific standard, all the contributions werereviewed by at least three researchers,and only 20 paperswere accepted and included in these proceedings. The papersare organized into sections on constraints, search,knowledge representation, temporal reasoning, planning,diagnosis and repair, and learning.