Book excerpt: When Organizations and Environments was originally issued in 1979, it increased interest in evolutionary explanations of organizational change. Since then, scholars and practitioners have widely cited the book for its innovative answer to this question: Under what conditions do organizations change? Aldrich achieves theoretical integration across 13 chapters by using an evolutionary model that captures the essential features of relations between organizations and their environments. This model explains organizational change by focusing on the processes of variation, selection, retention, and struggle. The "environment," as conceived by Aldrich, does not refer simply to elements "out there"—beyond a set of focal organizations—but rather to concentrations of resources, power, political domination, and most concretely, other organizations. Scholars using Aldrich's model have examined the societal context within which founders create organizations and whether those organizations survive or fail, rise to prominence, or sink into obscurity. A preface to the reprinted edition frames the utility of this classic for tomorrow's researchers and businesspeople.