Transfusion of blood [3.10] and Blood components[3.11] to subjects of care[3.51] is a medical activity that is subject to many legal regulations and constraints. Many problems may be encountered during treatment due to immunological conditions, transmitted diseases, sustainability and other difficulties. Mistakes and failures may have serious or even fatal consequences. Minimising human activity through the increased use of data processing and automated messaging will introduce an additional safety mechanism. This European Prestandard (prENV) specifies general messages[3.43] for electronic information interchange between computer systems used by healthcare [3.30] parties in the Blood transfusion [3.17] domain. The content and structure of the messages specified in this prENV have been developed with the aim of optimising the safety of Blood transfusion activity and to facilitate compliance monitoring and secure audit trails [3.4]. This European Prestandard is applicable to Blood transfusion related messages including those for: - the collection of blood from donor - preparation of Blood components - classification of Blood donations - dispensing of Blood components (to be transfused) to the recipient.