The author studies a reference from “The History of Faiyum and its Villages” (KitSb Ta’rikh al-Fayyum wa-bilаdihi) written by a high ranking Ayyubid official Abu ‘и^тап an-Nаbulus^ al-Safadr al-Shafi‘i (1192-1261) concerning the population of the Faiyum province. The author supposes that the majority of settled hadar communities mentioned by an-Nаbulus^ were Christians. Their population in the Faiyum by 1243 when an-Nаbulus^ composed his work, was 1142 adult males. Keeping in mind that by the seventh century when Egypt was conquered by the Arabs the Christian population of the Faiyum was something between 70 000 and 120 000 the author tries to answer the question of what the reasons were for such significant decrease, and considers three possible factors: Islamization of Egypt, when the country which was Christian in the seventh century turned by the fourteenth century into Muslim with a Coptic minority; natural disasters; “Bedouinization” of Faiyum, when the Copts might have been physically pushed out of the fertile lands of the province.