This article examines the institution of blood partnership, first theoretically, and then with reference to northern Equatorial Africa and Dar al-Kuti, a Muslim slave-raiding and slave-trading state. Contemporary anthropologists described blood partnership schematically as the exchange of blood and of conditional curses between two individuals or groups for the purpose of guaranteeing co-operation. They also suggested that blood partnership created bonds analogous to kinship. Blood alliances were concluded almost exclusively between parties who were not related genealogically, and promoted security, co-operation and long-distance trade. They were particularly important among societies outside highly centralized states, where they provided the ideology and mechanism for wider action embracing unrelated groups. Northern Equatorial Africa was just such an area, and, in the nineteenth century at least, blood pacts were very common. The article looks at blood partnership in the region generally, pointing out how foreigners, Muslims as well as Europeans, adopted the institution as a means of allying themselves with local leaders. Muslim penetration of the region is examined, and the infiltration of the zariba system of the southwestern Sudan into Ubangi-Shari (in what is now the Central African Empire) is outlined. The second half of the article deals specifically with Dar al-Kuti. Oral testimony and written evidence are combined to present a picture of blood partnership among the Banda, the most important non-Muslim people included in the state. The analysis is then extended to show how Muslims in the region, mainly the Runga from the Chad basin, led by Kobur and then by al-Sanusi, used blood pacts to foster their political and economic ambitions among non-Muslim peoples south of the Islamic frontier.