ENThe article is devoted to studying the role of the largest silver coin in monetary circulation, up to the end of the 60's of XVI century, in the Grand Duchy of Lithuania. The paper presents updated information on first mention of thaler in local sources. For various reasons, it was difficult for this coin to find its niche in the financial markets of GDL. This article also describes in details the first emissions of Lithuanian thalers, their features and characteristics. Keywords: GDL, thaler, groat, coin, Sigismund August, monetary circulation, treasure.