An analysis of the interplay between private entrepreneurship and government fiscal policies and procedures under Darius I of Persia, as exemplified by a member of the wealthy and prestigious Egibi family in Babylon, which had close business connections with government officials. Topics discussed include taxation, tolls, prebends, tax-farming, the international slave trade, market transportation systems, waterway usage, agricultural production, and other private and public economic processes. In addition, 143 pertinent texts are translated and commented upon. Autographed copies of previously unpublished texts are included.