During the colonial period, a handful of trading houses dominated the modern business sector of the Nigerian economy. These trading houses were collectively referred to as ‘The Old Mercantile Houses’ because of their long history of association with Nigeria dating back to the height of British imperialism in West Africa. Based on the colonial trade pattern featuring the importation of manufactured goods and general merchandise on the one hand, and the exportation of tropical produce and commodities on the other, these companies which were highly integrated dominated the Nigerian business landscape right from the colonial times until the 1960s when they were faced with intense competition from within and outside the country. In the process, these companies were forced to redeploy their enormous resources from colonial merchant trade into the establishment of several industrial plants and modern service enterprises, thus becoming conglomerates. They also became the pace setters on corporate organization and multidivisional structure. The chapter also highlights the opportunities and challenges which these companies had to contend with during the last two decades of the twentieth century and the first quarter of the twenty-first century as well as their current status in Nigeria.