The Ottoman censuses of 1885 and 1907, plus their related population registers, are a rich source of information on one of the lesser known aspects of the history of the Ottoman Empire. These documentary sources have hitherto only been used to produce totals for provinces and regions. Yet the registers are in fact an invaluable source for the study of fertility, marriage, and family structures in the collection of states and territories that made up the Ottoman Empire (which at this time comprised a large part of the Balkans and the Middle East). This article presents these two censuses and highlights their importance as documentary sources for the demographic and social history of this group of countries.