This volume in the series Documentary History of the Jews in Italy illustrates the history of the Jews in Sicily from 1415 to 1439. It is the sequel to the first three volumes and covers the events during the first half of the rule of King Alphonso the Magnanimous. The King took a personal interest in the affairs of the Jewish communities and exercised his authority through master Moyse Bonavogla, his personal physician, whom he appointed dienchelele, chief justice. During that period the Jewish minority of the island flourished economically and socially. Some 700 documents, many of them published here for the first time, record the fortunes of the Jews and their relationships with the authorities and their Christian neighbours. Much new information has come to light, and many facets of Jewish life in Sicily have been uncovered. The abundance of historical records in the archives of the Crown and of local authorities compares favourably with the relative scarcity of surviving documentation in earlier centuries. Therefore, again, many documents had to be reported in summary form. The volume is again provided with additional bibliography and indexes, while the introduction has been relegated to the end of the series on the Jews of the island.