The last years of the 20th Century have been somewhat contradictory with respect to values like loyalty, trust or truthfulness. On the one hand, (often implicitly, but sometimes very explicitly), self-interest narrowly defined seems to be the dominant force in the business world, both in theory and in practice. On the other hand, alliances, networks and other forms of cooperation have shown that self-interest has to be at least "enlightened".The academic literature has reflected both points of view, but frequently in (...) an ambiguous way, since the concepts of loyalty and trust are somewhat elusive and equivocal. This paper attempts to analyze the concept of loyalty in depth, examining the different conceptions about the word that can be found in the literature. We begin by going to the management classics (specifically, Follett, Barnard and Simon), and we then turn to the anthropological approach of Pérez López (1993), with its built-in ethical analysis, and show how trust and loyalty are crucial to the development of organizations. We end by suggesting in what ways loyalty and trust can be created and fostered in organizations. (shrink)