This paper will consist of an examination of the use of work contracts (mukatiba) and manumission contracts in the mid-16th century as an institutional tool for the economic and social integration of slaves into Ottoman Istanbul. The mukatiba contract was a legal device by which a slave was given a fixed period of time in which he was required to work, or alternately was assigned an amount of money (presumably to be earned through performing a job) that he had to produce before he was granted his freedom. Recorded in the Galata ?eriyye sicilleri (court registers) dating from roughly 1560-1570, numerous examples of mukatiba and other types of contracts for slaves from the Black Sea area, such as Ukraine, and the northern Mediterranean coast, primarily Italy and Spain, provide us with a wealth of detail as to how these slaves—who basically represent a wave of forced migration at a time when the growing imperial capital required new labor—lived, worked, converted, and were manumitted in early modern Istanbul. In addition, the slaves’ level of technical skill and the nature of their employment in Galata can also be ascertained from the sicills. The numerous mukatiba contracts, in combination with other types of entries in the sicills, such as manumission of slaves charitable reasons, suggest that the slave-owners of Galata considered it the norm to manumit their domestic and technically skilled slaves who had converted to Islam, and post-manumission possibly also integrated them into the greater household. While conversion to Islam and manumission from slavery do not necessarily signify complete ‘assimilation’ into society, this phenomenon does illuminate the slaves’ ability to negotiate their situation through the manipulation of Ottoman cultural and religious constructs which they have very clearly grasped and made their own. Thus, through analyzing the data provided by the ?eriyye sicilleri it is possible to come to meaningful conclusions about the nature of slaves’ assimilation into early modern Istanbul and the significance of their contribution to the social and economic fabric of this urban center.