African economic and social history since 1800 suggests that the relationships between ethnic consciousness and market transaction is very varied and largely unpredictable. The early twentieth century was a period of important change. Before 1900 labour was scarce and land abundant: inter-ethnic relations were relatively flexible, thanks to a general demand for mobile labour supplies. By 1960 population growth meant that property had become more valuable than labour: inter-ethnic relations became harder, thanks also to the way in which the colonial imposition of state structures had tended to institutionalise ethnic groups as units of political competition. Against this broad periodisation of social, economic, and political change, this chapter's case studies illustrate widely differing contexts and processes across African time and space. Much has depended on economic geography and on highly contingent historical circumstances, as also on the nature of the commodity traded in Africa's markets, whether labour (slave or free, skilled or unskilled), foodstuffs, cash crops, property, and political influence. While analysis of ethno-market relations in Africa has generally focused on 'horizontal' inequalities between ethno-regional groups, this chapter places equal, if not more, emphasis on changing 'vertical' social inequalities between persons or categories (gender, generation, class) within ethnic groups as a source of social unrest and political pressure. Internal, intra-ethnic tension over the 'moral economy' between the strong and the weak, rich and poor, can provoke a crisis of 'moral ethnicity', a sense of loss of moral community. This may provoke a crisis of 'political tribalism', as internal tension is dissipated in external competition. The contrast between the relative degree of internal tension within the Kikuyu and Luo peoples of Kenya provides an instructive case study of these possible connections between internal and external ethnic patriotisms. The chapter ends by proposing that Africa's history suggests that economists must look for more flexible, more agent-based, more class-conscious, models of possible ethnic relations with market economy than those that are currently relied upon.