"UNIDROIT Principles 2004" focused on an enlargement rather than a revision. An additional Section or Chapter so to speak, which are about, the Authority of a Agents, Third Party Rights, Set-off, Assignment of Rights, Transfer of Obligations and Assignment of Contracts, and Limitation Periods have been added, while the only change of substance made to the 1994 Edition, apart from two paragraphs in the Preamble, and three new provisions in Chapter 1 and 2 which are necessary to adapt the Principles to the needs of electronic contracting. The Principles which have the nature of the restatement of international uniform laws (for example CISG) are continuous exercise. Therefore we should note whether in the future our concerns would be on a additional topics on a improvement of the current text by monitoring the reception of the "UNIDROIT Principles 2004" in practice, and the application by contracting parties. The purposes of the Principles may be classified into three ; the rules of law governing the contract, means of interpreting and supplementing international uniform law or domestic law, or models for national and international legislator. Among them, the function of governing law may be applied by the express choice by the parties or by the implied choice like "general principles of law" or "les mercatoria", and it may be applied in the absence of any choice of law by the parties. Among there importance functions, this writer would like to emphasize the function to supplementing international uniform law instruments. The reason is that the CISG which has been established as an international uniform sales act and to which our country would be a contracting State from March, 2005, needs a lot of gap-filling. For this purpose it is advisable the parties to insert following provisions in their contract. "This contract shall be governed by the CISG, supplemented when necessary by the UNIDROIT Principles 2004" Thus success in practice of the UNIDROIT Principles over the last then years has surpassed the most optimistic expectations. It is hoped that the 2004 Edition of the UNIDROIT Principles will be just as favorably received by legislators, business persons, lawyers, arbitrators and judges and become even better known and more widely used throughout the World.