One important, but overlooked, risk mitigation device that facilitated the growth of the slave trade in the eighteenth century was the increasing availability of insurance for ships and their human cargoes. In this paper we explore, for the first time, the relative cost of insurance for British slave traders, the underlying processes by which this key aspect of the business of slavery was conducted, and the factors behind price and other changes over time. Comparisons are also drawn with the transatlantic slave trades of other nations. As well as analysing the business of underwriting slave voyages, the paper has two other objectives. First, we explore the meaning of slave insurance from the perspective of those directly involved in the trade. Was it about insuring lives or goods? Second, we provide new estimates of the importance of the slave trade to UK marine insurance. Did the former drive the growth of the latter, as Joseph Inikori has claimed?