Rather quietly over the last decade, a large body of literature has emerged to consider how new forms of organization arise and become established in the organizational community. The literature represents a very wide array of theoretical perspectives, and no emerging consensus or dominant theme can plausibly be identified. No long stream of research has been produced to validate the arguments of any perspective. What we find instead is a disparate group of mostly nascent theories from organizational ecology, economics, institutional sociology, strategic management, and others, all seeking to explicate the nature of contexts and processes that may generate new organizational forms. This review organizes this literature according to assumptions about how variations are generated in the organizational community. Three perspectives appear to capture most of the arguments: an organizational genetics view, which emphasizes random variation; an environmental conditioning view, which considers variation to be contextually constrained; and an emergent social systems view, which considers variations in organizational forms to be the products of embedded social-organizational interactions. Theories associated with each of the perspectives are explicated, and their practical implications for future research are examined. The review concludes with a brief consideration of the theory of the evolution of new organizational forms as itself an evolution of a new and important field of study.