Öz The consumption of substances such as coffee is known to have gained popularity in the early-modern period along with increased urbanization and the proliferation of public places such as coffeehouses, and bathhouses in towns. Marshall Hodgson refers to the use of such substances in the Venture of Islam, underlining their increase in popularity in the Islamic world, particularly following the Mongol era.[1] Boza is a sweet and fermented drink made from millet, chickpeas or barley, which is known to have equivalents in the Mediterranean, the Middle East, Crimea and the Balkans. Its consumption partly falls under the category of mood-changing substances along with alcoholic drinks as boza is alcoholic when fermented long enough. This article focuses on boza consumption in seventeenth-century Istanbul based on the travelogue of Evliya Çelebi. I compare this narrative with some aspects of my previous study of bozahane affairs in fifteenth-century Bursa, wherever the contents are relevant.[1] Marshall Hodgson, The Venture of Islam, II, 3 Vols. (Chicago: University of Chicago Press, 1974), 58-69.