This year, for the eighth time, the European Conference on Object-Oriented Programming (ECOOP) series, in cooperation with Springer, is glad to o?er the object-oriented research community the ECOOP 2004 Workshop Reader, a compendium of workshop reports pertaining to the ECOOP 2004 conference, held in Oslo from June 15 to 19, 2004. ECOOP 2004 hosted 19 high-quality workshops covering a large spectrum of hot research topics. These workshops were chosen through a tight peer review process following a speci?c call for proposals ending on November 30, 2003. We are very grateful to the members of the Workshop Selection Committee for their careful reviews and hard work to put together the excellent workshop program. We also want to thank all submitters, accepted or not, to whom the workshop program equally owes its quality. This selection process was then followed by a selection of workshop participants, done by each team of organizers based on an open call for position papers. This participant selection process ensured that we gathered the most active researchers in each workshop research area, and therefore a fruitful working meeting. Following the tradition of the ECOOP Workshop Reader, we strove for hi- quality, value-adding and open-ended workshop reports. The result, as you can judgefromthefollowingpages,isathought-provokingsnapshotofthecurrent- searchinobject-orientation,fullofpointersforfurtherexplorationofthecovered topics. We want to thank our workshop organizers who, despite the additional burden, did a great job in putting together these reports.