The articles in this special issue reflect some of the best papers from the IEEE Symposium On Logic In Computer Science held in Chicago in June 2005. There were many excellent papers, unfortuntaely not all could be selected and not all the papers selected were finally submitted to Logical Methods In Computer Science. Nevertheless, the four papers from among the submitted papers represent a good sample of the quality and diversity of the papers at the conference. In addition we have a fifth paper based on an invited talk by Solomon Feferman.

The papers were selected by the program chair in consultation with some members of the program committee and other members of the community. There was strong agreement on the papers chosen.

The paper by Masahito Hasegawa on Relational Parametricity and Control and the paper by Lars Birkedal, Noah Torp-Smith and Hongseok Yang on Semantics of Separation-Logic Typing and Higher-order Frame Rules for Algol-like Languages represent some of the best work in the theory of programming languages in recent years. It is very gratifying to find that LICS is considered a desirable venue for such papers.

LICS has always had a strong representation in finite model theory and complexity. The paper Generalized Majority-Minority Operations are Tractable by Victor Dalmau was an easy choice this year. The paper On the decidability and complexity of Metric Temporal Logic over finite words by Joel O. Ouaknine and James B. Worrell settles several open problems in the field of model checking and verification.

The LICS conference had a classic new result in finite model theory by Ben Rossman, winner of the Kleene award. Unfortunately his paper had already been promised to another journal.

I am delighted that the invited talk by Solomon Feferman on Tarski's influence on Computer Science led to a paper for this special issue. The talk was inspiring and the accompanying paper is a must read for all theoretical computer scientists.