This article is based on letters from the Geniza. The writers were merchants who dealt in imports and exports between Egypt and other countries of the Mediterranean basin. These merchants were part of the Jewish elite and maintained close ties with the Muslim authorities. They enjoyed considerable status with these authorities, who co-operated with the merchants, especially in the transport of goods; some of the high officials were, in fact, ship-owners. The administration of the time took a great interest in imports and exports, and would at times confiscate goods required by the army. The article reviews a series of citations from letters thus examining the relationship between the merchants and the authorities. The second part deals with the evidence of the droughts found in the merchants' letters; it is interesting to compare the details on droughts with the information in the Arabic sources. The third part discusses the information contained in the Geniza documents on the conquest of Jerusalem (638). This is followed by a discussion of two figures who are also known from Arabic sources: Manasseh b. Abraham Ibn al-Qazza¯z, and Barjawa¯n. The letters also reflect the restrictive measures against Jews and Christians in the days of Caliph al-Ha¯kim.