Parts I and II
These two volumes dedicate themselves above all to the formation of contracts, validity, performance and remedies for non-performance, i.e. themes that are well developed in comparative law literature. Part I of these principles was released in 1995 (see Reinhard Zimmermann, Konturen eines europäischen Vertragsrechts, Juristenzeitung 1995, p. 477, ff.). Part II was completed in 1996 and published in 2000.
 
Part III
Part III focuses upon general contract law questions that have only seldom been addressed from a comparative law perspective (prescription, set-off, plurality of debtors, illegality, unconscionability, conditions and capitalisation interest) but whose treatment is nonetheless essential in a work on the foundations of a common European law of contract. Towards this end, the Lando-Commission decided in its last session to carry forward the work of Part II. In 1996 at a meeting in Stockholm, the Commission on European Contract Law was thus newly constituted and its working plan was devised. Current and former members of the commission include:
 
Christian von Bar (Osnabrück)
Hugh Beale ( through 2000) (Warwick)
Marc Elvinger (through 1999) (Luxemburg)
Michael Joachim Bonell (Rome)
Michael Bridge (London)
Carlo Castronovo (Milan)
Eric Clive (since 2000) (Edinburgh)
Ulrich Drobnig (Hamburg)
Carlos Ferreira de Almeida (Lisbon)
Sir Roy Goode (Oxford)
Arthur Hartkamp (Den Haag)
Ewoud Hondius (Utrecht)
Konstantinos Kerameus (Athens)
Ole Lando (Copenhagen)
Hector MacQueen (Edinburgh)
Fernando Martinez Sanz (Castellón)
Bryan McMahon (Dublin)
Willibald Posch (Graz)
André Prüm (since 1999) (Nancy)
Jan Ramberg (Stockholm)
Matthias E. Storme (Ghent)
Denis Tallon (Paris)
Thomas Wilhelmsson (Helsinki)
Claude Witz (Saarbrücken)
Reinhard Zimmermann (Hamburg)
 
The Principles were compiled in five plenary meetings occurring respectively in Regensburg, Edinburgh, Graz, Regensburg and Copenhagen. At these meetings the draft formulations of the individual Reporters were debated. Reporters for the individual subject areas were: 
 
Ulrich Drobnig (Capitalisation Interest)
Roy Goode (Assignment of Claims)
Willibald Posch (Substitution of New Debtor and Transfer of Contract)
Dennis Tallon and Claudia Witz (plurality of debtors and creditors)
Michael Bridge (Conditions)
Hector MacQueen (Unconscionability and Illegality)
Reinhard Zimmermann (Set-off and Prescription).  
 
The plenary meetings were accompanied by smaller steering committee meetings which sometimes included the reporters for the individual subject areas. The Principles of European Contract Law, Part III, was debated and adopted at the last meeting of the Lando-Commission in Copenhagen in February 2001. An editing committee that had been selected by the Commission, comprising Ole Lando, Andre Prum, Eric Clive and Reinhard Zimmermann, prepared the text for publication. As with Parts I and II, Part III was published by Kluwer Law International in 2003; along with the Principles the work contains a commentary on the provisions as well as comparative law analysis.
 
Translation of the Principles of European Contract Law
A German translation of Parts I and II was completed by Ulrich Drobnig, Hartmut Wicke and Reinhard Zimmermann; this translation first appeared in the Zeitschrift für Europäisches Privatrecht (ZEuP) 2000, page 675 ff. Subsequently, Christian von Bar and Reinhard Zimmermann completed a translation of the aggregate materials from Parts I and II (articles of law, commentaries and annotated comparative law analysis); this translation was published by Sellier European Law Publishers in 2002. These same authors prepared a translation of Part III that in 2005 was also released by Sellier European Law Publishers. This volume relies on the translation of the Principles by Ulrich Drobnig, Reinhard Zimmermann and Jan Kleinheisterkamp which appeared in ZEuP 11(2003), page 895 ff. In addition to the provisions themselves, the translation of Part III by Christian von Bar and Reinhard Zimmermann also incorporates commentaries and comparative law remarks.  
 
The comparative law position papers prepared by Reinhard Zimmermann as part of his work on the Lando-Commission led to the development of three articles which, together with an introduction, were published as a book in 2002: Reinhard Zimmermann, Comparative Foundations of a European Law of Set-Off and Prescription, Cambridge University Press, 2002 (a work in conjunction with the Goodhart Lecture Series and in gratitude to the University of Cambridge for the 1988/99 appointment as Goodhart Professor of Legal Science).
 
Principles of European Contract Law and Europeanisation of Private Law
The preparation of a common frame of reference represents the initial steps towards a unified European law of contracts that could in the long run yield a European codification of contract law. As such, the Principles of European Contract Law along with the Unidroit Principles of International Commercial Contracts constitute a noteworthy contribution by their presentation of suggested provisions that have been prepared at the international level and that are accessible via a common frame of reference. However, the Principles of European Contract Law also have great potential significance in respect of further development within the national legal systems in EU Member-States. Specifically, they denote the contours of a new ius commune and can serve a function resembling that of their historic predecessors. For more on this topic: Reinhard Zimmermann, "Ius Commune and the Principles of European Contract Law: Contemporary Renewal of an Old Idea", in: Hector L. MacQueen, Reinhard Zimmermann (eds.), European Contract Law: Scots and South African Perspectives, Edinburgh University Press, 2006, p. 1 ff.