Purpose - As specialisation takes root in human communities, the economics of scale and of diversity come into play. Scale leads to product markets, specialised firms, channels, and to industries. Diversity generates peasant markets, shopping malls, and business eco-systems. These outcomes are all examples of marketing systems, and are typical of the patterns that emerge, grow, adapt and evolve in complex transaction flows. Marketing systems are multi-level, path dependent, dynamic systems, embedded within a social matrix, and interacting with institutional and knowledge environments. The purpose of this paper is to outline a number of propositions that might serve as a basis for a theory of marketing systems. Design/methodology/approach - The paper draws on historical research into the evolution of exchange and on examples of markets and exchange practices from marketing, anthropology, sociology, and economics. It utilises results from complex adaptive systems theory, from the networks and markets literatures, and from ecology, to formulate a series of propositions that identify properties believed to be common to all marketing systems. Findings - Marketing systems are identified and categorized as emergent patterns in flows of transactions. In total, 12 foundational propositions are suggested. The propositions are complementary to those suggested by S-D logic. Originality/value - This paper offers a fresh approach to the study of marketing systems, developing relevant theory. Marketing systems link micro choices with macro outcomes, with implications ranging from disaster recovery to distributive justice and QOL outcomes.