Over the past decade the legal-administrative framework of United States air pollution regulation has changed from one based almost entirely on “command control” mechanisms to one allowing considerable use of “transferrable pollution permits.” This article traces the process of that change, suggests why it may be a very significant one, and proposes a social explanation for it. Perhaps its most important explanatory proposition is that market mechanism regulation may reflect the formation and rise of a new “regulatory culture” likely to affect the form and substance of regulation more generally.