Special issue of the journal Thermal Science dedicated to Dubrovnik Conference on Sustainable Development become already traditional. Present issue, Vol. 14, No. 3, 2010, is the 4th one, and contains selected papers presented at the 5th Dubrovnik Conference on Sustainable Development of Energy, Water, and Environment Systems, held from September 30 to October 3, 2009, in Dubrovnik, Croatia. 5th Dubrovnik Conference was held in the shadow of the new European Energy policy, formulated in short as: "a new energy-climate pack age of measures, reaching for obligatory targets of 20% renewable energy in gross consumption, 10% renewable fuels in transport, 20% decrease of greenhouse gases emissions, and 20% in crease of energy efficiency by 2020". Considering this fact, selection of the papers for this issue has the aim to show the reflection of this process on the energy policy and practice in the countries of the South East European region (SEE region). Selection of papers presented at the 5th Dubrovnik Conference, done by Guest editors, clearly shows that countries of the SEE region, depending on specific energy and economic conditions, made great efforts to follow recommendations of the new European energy policy, and to meet challenges of climate changes, and at the same time to in crease security of energy supply. I am deeply grateful to the Guest editors, Professors Neven Duić, Zvonimir Guzović, and Daniel R. Schneider, for excellent paper selection, the job which is at the same time highly professional and delicate. I am sure, that readers will obtain realistic insight in the policies, activities, achievements, results, and barriers, existing in most of the countries in the South East European region, along their movement towards sustainable development. Having in mind in creased interest in research and engineering activities aimed to "improvement and dissemination of knowledge on methods, policies, and technologies for increasing the sustainability of development", Editorial Board considered interesting to add several papers in Part II of this issue, not presented at Dubrovnik Conference, but dealing with the problems of sustainable development as well. We believe that those papers will give even wider picture of the efforts undertaking in the countries of the South East European region to achieve sustainable energy systems. At least, but not last, its my pleasure to put your attention to the fact that in this year our journal Thermal Science obtained his first official Impact factor (0.407), at the official citation list of Thompson Scientific. I am deeply grate ful to all authors, review ers, members of our Editorial Boards and International Scientific Board, for their contribution to this success, after 15 years of publishing this journal. I hope that number and quality of the papers published in the journal Thermal Science will increase further, and that our papers will be cited more and more, leading to the respectable position of the journal among large group of scientific journals world wide. Considering every day larger and larger number of papers of high quality submitted, and accepted, for publication in the journal, we decided to open Online First list on our web site. http://thermalscience.vinca.rs/online-first Online First list will contain the final versions of articles that have been accepted for publication, but have not yet appeared in the paper journal. Papers will appear on Online First list at the moment of acceptance for publication, just after passing peer reviews. Online First articles can be found on the Internet and cited by their digital object identifiers (DOIs). At the same time, Online First list of the papers accepted for publication in the journal Thermal Science can be seen on the offi cial web site of the National library of Serbia http://www.doiserbia.nb.rs/issue.aspx?issueid=1053 Prof. Dr. Sim eon Oka Editor-in-chief