This special issue includes a selection of papers from the Koli Calling conference, the Fourth Finnish / Baltic Conference on Computer Science Education, organized by the University of Joensuu at Koli, Finland, in October 1-3, 2004.

The Koli Calling conference has been organized yearly since 2001. Its primary goal is to promote the development of computer science education (CSE) and CSE research. The call for papers has been internationally distributed already from the beginning, and we have had a few foreign presentations each year. However, during the first three years the conference could still be characterized as a meeting of Finnish CS educators and CSE researchers to present their research work and experiences of novel tools and ideas in CS education.

In 2004, the program committee decided to promote the scientific level of the conference and widen its international visibility by applying some changes in the conference organization. Consequently the number of submissions was doubled and we finally got 37 participants from 7 countries.

The actions taken were the following. First, the call for papers of the conference now included two categories, discussion papers and research papers, to make a clearer distinction between papers that present novel ideas, approaches and systems for CS education, and papers in which these issues have been elaborated further in some rigid research setting. Both types of papers are equally necessary for the CS education community, but they have different roles. New ideas and tools are the fuel for research work, and research is needed to convince us that we are really making progress towards our goal of improving learning. Second, the review process of the conference was tuned so that each paper was reviewed by three PC members. Each paper was reviewed by PC members from at least 2 different countries, and no one reviewed papers that were submitted from his/her own institute. Third, we decided to publish the extended versions of the best research papers in this journal. We were happy to agree with Valentina Dagiene that a special issue of the conference would be published in Informatics in Education in 2005.

The six papers in this issue were selected among the best research papers presented in the conference based on the original conference reviews and the preference of the journal executive editor. The authors of the papers were asked to extend the papers before submitting them to the journal. Thereafter two reviewers, one from the journal editorial board and one from Koli Calling PC carefully reviewed the extended versions, and the authors were requested to revise the papers based on the comments. The final papers are included in this issue.