The rules presented in this volume of the "Principles of European Law" deal with sales contracts. The sales contact has served as the paradigm for contracts in general. Moreover, it is also probably the most common contract, and certainly the most common consumer contract, that there is. In fact, sales come in all shapes and sizes: ranging from the purchase of the daily newspaper at the news-stand or the groceries in the supermarket, through to the purchase of a new car and to commodity sales on highly specialised markets. Furthermore, there are many mixed transactions that contain a certain element of sale, such as distribution contracts or all sorts or manufacturing contracts. These Principles start from the idea of a uniform regime for all kind of sales transactions. Moreover, these Principles aim to meet the needs of international and national commerce alike and attempt to create a truly uniform sales law, bridging the differentiation into different settings, different parties to the contract, and different object of sales. However, when deemed necessary certain provisions are declared mandatory in consumer sales, in order to protect the weaker party in the transaction involved. To that end, a balance is struck between the two major international instruments in this area, the CISG and the Consumer Sales Directive. Moreover, during the drafting process, comparative material from over 20 different EU Member States has been taken into account. The work therefore is not only a presentation of a future model for European rules to come but provides also a fairly detailed indication of the present legal situation in the Member States. The Study Group on a European Civil Code has taken upon itself the task of drafting common European principles for the most important aspects of the law of obligations and for certain parts of the law of property in movables which are especially relevant for the functioning of the common market. Like the Commission on European Contract Law's "Principles of European Contract Law", the results of the research conducted by the Study Group on a European Civil Code seek to advance the process of Europeanisation of private law. Among other topics the series tackles sales and service contracts, distribution contracts and security rights, renting contracts and loan agreements, negotiorum gestio, delicts and unjustified enrichment law, transfer of property, and trust law. The principles furnish each of the national jurisdictions a grid reference. They could be agreed upon by the parties within the framework of the rules of private international law. They may provide a stimulus to both the national and European legislator for moulding private law. Beyond this, they aim to further discussion about the creation of a European Civil Code, or a Common Frame of Reference in the area of patrimonial law, by submitting a concrete model.