This book constitutes the thoroughly refereed post-proceedings of the Third International Workshop on Scientific Engineering of Distributed Java Applications, FIDJI 2003, held in Luxembourg-Kirchberg, Luxembourg in November 2003.The 213 revised full papers presented together with abstracts of two invited contributions were carefully selected during two round of reviewing and revision from 29 submissions. Among the topics addressed are Java-enabled service gateways, mobility in distributed settings, XML, embedded Java software, interception services, mobile agents, error management, software model engineering, distributed composite objects, cooperative applications, distributed mobile applications, service-based software architectures, and distributed Java programs.