Keywords Omni-channel; Retail-mix; Retail performance; Online Abstract The world of retailing has changed dramatically in the past decade. The advent of the online channel and new additional digital channels such as mobile channels and social media have changed retail business models, the execution of the retail mix, and shopper behavior. Whereas multi-channel was in vogue in the last decade in retailing, we now observe a move to so-called omni-channel retailing. Omni-channel retailing is taking a broader perspective on channels and how shoppers are influenced and move through channels in their search and buying process. We discuss this development conceptually and subsequently discuss existing research in this multi-channel retailing. We also introduce the articles in this special issue on multi-channel retailing and position these articles in the new omni-channel movement. We end with putting forward a research agenda to further guide future research in this area. Author Affiliation: (a) University of Groningen, Faculty of Economics and Business, The Netherlands (b) University of Maryland, Smith School of Business, United States (c) University of Pittsburgh, Joseph M. Katz Graduate School of Business, United States * Corresponding author at: University of Groningen, Faculty of Economics and Business, Department of Marketing, Duisenberg Building 329, P.O. Box 800, NL-9700 AV Groningen, The Netherlands. Tel.: +31 50 363 7320. (footnote)[white star] The authors acknowledge the supportive comments on an earlier version of this paper given by Murali Mantrala and Steven Brown editors of the Journal of Retailing. Byline: Peter C. Verhoef [p.c.verhoef@rug.nl] (a,*), P.K. Kannan (b), J. Jeffrey Inman (c)