Although the notion of “informality” only appeared in social sciences and international institutions in the seventies, the practices to which it refers have been drawing attention from social scientists for more than sixty years. What part did anthropology play in the effort to conceptualize these practices defined by their distance from social norms? Even though anthropologists actively contributed to the debates from which the concept of “informality” emerged, it nevertheless seemed to them that this notion was not appropriate to the study of the practices concerned; whence the consequent proliferation of other concepts such as “solidarity-based economy” or “popular economy.” A new interest in the “informal sector” has emerged over recent years, but this new research bears as much upon the notion of “informality” and what it teaches us about the making of economic rules as upon “informal practices” themselves.