The introductory part of this paper examines an increasingly popular catchword Ecocity as a brand of ecological city that has been adopted by many cities all over the world. The authors depict development of the Ecocity movement, which seeks for ecologically healthy and compact cities, proving coincidence with ideas of the theoretical concept of New Urbanism. They further investigate compatibility of the term Ecocity with ideas represented by the concept of sustainable city. Ecocity as an international research project supported by the European Commission is a subject of the second part of the paper. It contains essential information on the project methodology, organising structures, and scientific objectives as well as the project’s relationship to objectives, policies and initiatives of the EU in the field of sustainable urban development. The project is aimed to put forward its own vision of a sustainable city of the third millennium, which should also demonstrate its feasibility under special conditions of seven selected model areas. Though the project follows a holistic approach to sustainability, special emphasis is given to issues of sustainable transport. This reflects a fact that mobility of people and goods has a central impact on the quality of urban environment. Finally, one of the Ecocity project model areas, located in the historic city Trnava, is briefly introduced.