The practice of parents and their young children co-sleeping is a topic of ongoing controversy and debate. Both physical and psychosocial risks and benefits have been attached to this practice. In this introduction to the special issue, we present the prevailing views about early sleep arrangements. We then discuss the organization of the special issue and highlight the contributions of each article. Together, this collection of original articles comprises a body of research that advances our understanding of co-sleeping in the context of social and physical environments. Copyright © 2007 John Wiley & Sons, Ltd.