Zoroastrian theology, cosmology and cosmogony, history of the faith, its rituals and ceremonies, Avestan and Middle Persian texts, festivals such as Nowruz, Mehregan and Sada, and a host of other topics, hitherto dispersed amidst other entries in their alphabetical sequence in the Encyclopædia Iranica, are gathered together here under one cover. The volume enables the readers to chart their way through complex traditions and debates throughout history, and brings into focus the interdependence of these pioneering contributions. As a thought-provoking and authoritative work of reference, it is a testimony to the fine scholarship and remarkable erudition of its contributors, scholars who have been foremost in ensuring that the Encyclopædia Iranica maintains its high reputation for authoritative comprehensiveness and pioneering research.