We welcome you to Coordination ’99, the third in a series of conferences d- icated to an important perspective on the development of complex software systems. That perspective is shared by a growing community of researchers – terested in models, languages, and implementation techniques for coordination. The last decade has seen the emergence of a class of models and languages variously termed "coordination languages", "con?guration languages", "arc- tectural description languages", and "agent-oriented programming languages". Theseformalismsprovideacleanseparationbetweenindividualsoftwarecom- nents and their interaction within the overall software organization. This se- ration makes complex applications more tractable, supports global analysis, and enhances the reuse of software components. The proceedings of the previous two conferences on this topic were published by Springer as Lecture Notes in Computer Science 1061 and 1282. This issue of LNCS containing the papers presented at Coordination ’99 continues the tradition of carefully selected and high quality papers representing the state of the artin coordinationtechnology.In responseto thecallfor papers, wereceived 67 submissions, from which 26 papers were accepted. These proceedings also contain abstracts for posters presented at the conference. This year’s program features invited talks by Rocco De Nicola and Danny B. Lange. Reading through the papers, we expect that you may be surprised by the variety of disciplines within computer science that have embraced the notion of coordination. In fact, we expect this trend to continue, and hope that you will contribute to the on-going exploration of its strengths, weaknesses, and applications.