This chapter presents an overview of recent developments in online delivery of tourism services, highlighting major issues and challenges. Many tourism services are highly amenable to online delivery and, in OECD countries, the adoption of e-commerce and online service delivery in tourism has been rapid. The tourism sector is among the leaders in online marketing and sales, but considerable potential remains, with the sector lagging in the adoption of supply chain related systems and the use of ICTs for internal efficiency. The Internet brings new opportunities and challenges, with both disintermediation and the emergence of new intermediaries. Key policy issues include the need to carefully monitor the competition effects of online service delivery and take advantage of the potential for the development of destination management systems that provide an integrated front-end for small to medium sized tourism enterprises.