Although the overall investment in information technology (IT) decreased during the first few years of the 21st century, B2B e-commerce continued to expand at a rapid rate (Lim & Wen, 2002). The expansion of B2B e-commerce has been based to a large extent on accounting and enterprise-wide information systems (EISs) that permit electronic data transmission and execution of transactions in an effective and efficient manner. Since B2B e-commerce is Internet based, the EISs required to support B2B e-commerce must be Internet capable. The primary language of the Internet, Hyper-text Mark-up Language (HTML), is not well-suited for transmitting data and executing transactions. Consequently, Extensible Mark-up Language (XML) was developed to facilitate a wide range of electronic information exchange applications, including many applications related to B2B e-commerce. XML also allows legacy data to be accessed through the Internet. As initially conceived, XML had a number of constraints, particularly in the area of data integrity and security; however, these constraints are being overcome. This article discusses the objectives of using XML in B2B e-commerce, reviews the technical structure of XML, and discusses ways that data integrity can be maintained and security enhanced while engaging in B2B e-commerce.