This fourth paper, in a series on the theme of the informal economy, considers the extent to which premodern trade in Melanesia constituted any preparation for engagement with the market. It reviews explanations of trade and exchange in ‘aboriginal’ societies, from Adam Smith in the eighteenth century and the German historical school in the nineteenth, to their modern heirs and critics. The view of trade as due to a natural human tendency to ‘truck and barter’ is counter-posed against a conception of exchange as the product of socially regulated customs, in the manner of The Gift. Malinowski’s account of the kula, and its (mis)interpretation by Van Leur, the historian of Asian trade, raises the question whether Melanesia possessed any counterpart of the travelling Asian peddler. To consider this question, the paper examines the traditional trading systems of regions which would later become the hinterlands of three modern towns (Rabaul, Port Moresby and Goroka). In preparation for later discussion of these towns’ colonial experience, the paper surveys the traditional trade of the New Guinea interior, the long-distance seaborne trade of the coasts and islands, and the particular case of the Gazelle Peninsula. It draws conclusions which throw some light on the question of Asian-style ‘peddling’ in Melanesia. Finally, the paper considers how Keith Hart’s concept of ‘informality’, derived from Weber’s notion of rational/legal bureaucracy, could be seen as applicable to the early colonial setting of New Guinea. It finds a piquant correspondence between a highly bureaucratized German New Guinea and the Weberian original, located back in Bismarck’s Berlin.