The present study is a grammatical description of the Arabic dialect of the Jews of Tripoli (Libya). Jews in North Africa adopted Arabic as their native speech during the first (pre-Hilalian) period and their dialects therefore preserve archaic features no longer present in the dialects of their Muslim neighbours. The Jewish dialects are also distinguished by the use of many words of Hebrew and Aramaic origin. In Tripoli the difference between the Jewish and Muslim vernaculars manifests itself not only in the vocabulary but also in the language type: The Jewish dialect represents the sedentary type while the Muslim dialect belongs to the Bedouin type. After the immigration of Tripolitanian Jewry to Israel the use of the Arabic dialect has become reduced, and it is estimated that the youngest generation who can still speak it is in their forties. It is obvious, therefore, that in a few decades the Arabic dialect of the Jews of Tripoli, like other Judaeo-Arabic vernaculars, will cease to exist. The present study which also contains texts and a glossary may contribute to preserving a vanishing Arabic dialect.