The slave trade, death, and misery were inseparable long before abolitionist writers took up the slave trade as a subject in the late eighteenth century. Throughout the historiography there has been widespread recognition that Africans entering the trade died not only during the middle passage but during the process of enslavement and travel in the interior, on the African littoral awaiting shipment, and after arrival in the Americas. Europeans directly involved in the traffic were at risk in the last three of these four phases of transition between life in Africa and life in the Americas, and tended to die at rates comparable to their human cargoes. In the shipboard phase, and probably also in other stages of the journey, mortality in the slave trade normally exceeded that in other long-distance population movements. In the nineteenth century this differential widened as rates on other long-distance routes fell (Cohn, 1984; Eltis, 1984; Grubb, 1987; Klein, 1978; McDonald and Shlomowitz, 1989, forthcoming). To date, most explanations have focused on morbidity and mortality on board ship; data on the preembarkation phases are no more available to us today than to the abolitionists 150 years ago. For shipboard mortality, overcrowding on the ship, psychic shock, and violence have not fared well as explanations in the work of the last two decades, although the interplay between the first two and resistance to disease suggests further consideration. The present study focuses on shipboard mortality, but it is based on a large and complex dataset. It begins with a discussion and preliminary analysis of the nineteenth-century data. This is followed by a review of the various hypotheses on mortality in the slave trade.