This special issue of Logical Methods in Computer Science (LMCS) contains extended and revised versions of selected papers first presented at the 19th Annual IEEE Symposium on Logic in Computer Science (LICS 2004), held July 13-17, 2004 in Turku, Finland.

This issue is dedicated to the LICS 2004 program chair, Harald Ganzinger, who passed away on June 3rd, 2004. Although he had been in poor health for quite some time, Harald made a valiant effort to guide the LICS 2004 Program Committee through the selection of the papers for the symposium.

In consultation with the LICS 2004 Program Committee, a small number of papers presented at the symposium were selected, and their authors were invited to submit full versions to this special issue. All submissions were refereed in accordance with the usual high standards of LMCS. The papers in this special issue span different topics within logic in computer science, reflecting well the quality, technical depth, and broad range of LICS. I am grateful to the authors of the papers for their excellent contributions, to the members of the LICS 2004 Program Committee, to the reviewers for their efforts, and to the managing editors of LMCS, Dana S. Scott, Gordon D. Plotkin, Moshe Y. Vardi and Jiri Adamek, for their help and guidance throughout this process.