ENThe articles deals with the medieval sources on the history of the Karaites who appeared in the Grand Duchy of Lithuania during the reign of duke Vitold (Vytautas). Many of them were already analyzed by researchers, whoever some questions still remained unanswered or presented not always in fully critical way. The research questions deal with the original privilege issued by Lithuanian monarchs to the Karaites, allegedly participation of the Karaites at the battle of Tannenberg or travel description left by Burgundian knight Gilbert de Lannoy. It seems that the first written document, shaping he legal position of the Karaites in the Grand Duchy of Lithuania was issued by duke Casimir Jagellonides in 1441. The charter of grand duke Vitold, drawn in 1388, was certainly forged sometime in the 15th century. The Bavarian Latin chronicle informing that a Jewish (in fact, Karaite?) military unit supported Polish-Lithuanian army at the battle of Tannenberg in 1410, transmitted only political propaganda, and did not reflect a real fact. Famous Burgundian traveler, who visited Grand Duchy of Lithuania in the beginning of the 15th century, met Karaites in Troki. Keywords Medieval Karaims, Grand Duchy of Lithuania, settlement. [From the publication]