This volume presents the proceedings of the 6th Portuguese Conference on Artificial Intelligence, EPIA '93, organized by the Portuguese Artificial Intelligence Association. Like the last two conferences in this series, it was run as an international event with strict requirements as to the quality of accepted submissions. Fifty-one submissions were receivedfrom 9 countries, the largest numbers coming from Portugal (18), Germany (10), and France (8). The volume contains 25 selected papers, together with 7 poster abstracts and one invited lecture: "Organizations as complex, dynamic design problems" by L. Gasser, I. Hulthage, B. Leverich, J. Lieb, and A. Majchrzak, all from the University of Southern California. The papersare grouped into parts on: distributed artificial intelligence, natural language processing, knowledge representation, logic programming, non-standard logics, automated reasoning, constraints, planning, and learning.