jats:titleAbstract</jats:title> jats:pIn the Middle Ages the Karaite Jews in the Islamic world used both Arabic and Hebrew script in their writings. They wrote not only Arabic texts in Arabic script but also many of their Hebrew Bibles in Arabic transcription. The Rabbanites, by contrast, used Hebrew script for writing both Arabic and Hebrew. This paper examines the association of the Karaites with the Masoretic transmission of the Hebrew Bible and the motivation for their transcribing the Bible into Arabic script. It is argued that the Arabic transcriptions reflect the polemical stance of the Karaites against the bases of scriptural authority of the Rabbinites and an advanced degree of rapprochement of the Karaites with the Muslim environment. They represent a convergence with the external form of the Muslim Arabic Qurʾān and also with the concepts of authority associated with the transmission of Muslim scripture.</jats:p>