This chapter, written from the developer’s point of view, starts with an overview of the challenges of building automatic translation systems, i.e. how to encode and organize all language information and world knowledge. Added to these “hard” problems, is the question of how to make to make a system useful. This chapter explores, first, how an MT system is created; and second, what the ongoing relationship is between developers and users. The first part broaches the following topics: rule-based MT development, information resources, data-driven MT development, the language coverage and a typology of the MT systems. The next part discusses the performance of MT systems, and the strategies employed by developers and users to improve the quality of MT output. The final part deals with the questions of who actually uses MT systems; how MT systems can be commercially successful; and why translators are often averse to MT.