Ten states and the District of Columbia prohibit payday loan stores, and thirty-one other states have imposed regulatory restraints on their operations, ranging from limits on fees and loan amounts to the number of rollovers and renewals allowed a borrower. Given the importance of payday lenders to significant segments of the population and the wide variation among state regulatory regimes, our paper examines the extent to which the concentration of payday lenders in counties throughout the country is related to the regulatory environment as well as to various financial and demographic factors. The analysis is based on a unique dataset that has been obtained directly from each state's appropriate regulatory authority. (C) 2015 The Authors. Published by Elsevier Inc.