The Prosopography of the Middle Byzantine Period is a comprehensive biographical dictionary for the Eastern Mediterranean, including Byzantine Italy, in the Early Middle Ages. Itis published in two sectionsand documents over 21,000 people. The first section covers the period from 641 to 867, the second extends to 1025. Apart from the main volumes, each section contains an additional introductory volume, Prolegomena, containing principally information about the most important sources for the period - both Byzantine and non-Byzantine - together with a concluding volume with the definitive list of abbreviations, the indexes, and addenda and corrigenda. The work covers firstly all Byzantines mentioned either by name or anonymously in the relevant Byzantine and non-Byzantine sources, and secondly all persons mentioned in the Byzantine sources both from Western Europe and from the Arabic and Slavonic areas, together with those from the Christian East. The articles on the individual people bring together all known details in each case and give information on the present state of research. Both sections contain comprehensive indexes of names, variants of names, offices, titles, places and geographical terms, which facilitate use of the work. A subject index and online versions of all the indexes are in preparation. Thus the Prosopography is a research instrument of use both to the specialist and to all those just looking for rapid information on individuals, a region or a particular event.