The Islamic Republic of Iran's parliament, the Majlis, passed in 1990 a law setting out the functions of its national library. In 2005, the inauguration of the first stage of the new national library building was celebrated as a major national cultural and architectural achievement. This article looks at the origins and evolution of the National Library of Iran (NLI), considers its changing place within the Iranian library system, and also briefly considers what scope it has for developing. It also examines the nature of the new building, asking how well it is designed to implement the guidelines laid down by the Majlis and what scope and flexibility it allows for future developments. (Contains 9 notes.)