We study a period of Javanese history when the consumption of opium was legal, but the supply of it was undergoing substantial institutional transformation. Through most of the nineteenth century the opium trade was organized into a system of “revenue farms,” which were privately owned local monopolies that bought raw opium from the government, refined it, and sold it to consumers. After 1893 this system was replaced by a government monopoly, the so-called opium regie, which controlled importation, refining, and retailing. Our main conclusion is that this change in policy substantially reduced opium consumption.