In this paper, the author addresses the question ‘what is so special about Esperanto that a prestige-sensitive software company chose to adopt it?’. The first section gives a short history of how Esperanto became involved in machine translation. The second section prepares the discussion about Esperanto as an intermediate language, explaining why an intermediate language is needed at all. The third section points out that the choice of an intermediate language is conditioned by the basic design of the machine translation system. The fourth section discusses the virtues and drawbacks of alternative intermediate representations, and the fifth section shows under which circumstances the best choice is Esperanto. The final section describes in greater detail those properties of Esperanto that make it particularly suitable for functioning within a machine translation system.