EOOLT'2007 was the first edition of the ECOOP-EOOLT workshop. The workshop is intended to bring researchers associated with different equation-based object-oriented (EOO) modeling languages and different application areas making use of such languages together. The aim of the workshop is to explore common grounds and derive software design principles that may make future EOO modeling languages more robust, more versatile, and more widely accepted among the various stakeholders. At EOOLT'2007, nineteen researchers with diverse backgrounds and needs came together to present and discuss fourteen different concept papers grouped into the four topic areas of integrated system modeling approaches; hybrid modeling and variable structure systems; modeling languages, specification, and language comparison; and tools and methods. 1 Objectives and Call for Papers Computer aided modeling and simulation of complex systems, using components from multiple application domains, such as electri...