This book constitutes the refereed proceedings of the 14th European Conference on Object-Oriented programming, ECOOP 2000, held in Sophia, Antipolis and Cannes, France, in June 2000. The book also contains a CD-ROM providing digitized versions of all previous ECOOP conference proceedings and related indices. The 20 revised full papers presented in the book together with 3 invited papers were carefully reviewed and selected from a total of 109 submissions. The book is divided into topical sections on UML, type theory, object relations, cooperation and distribution, Java run time, optimization, and tools.