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 the 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 book s interdisciplinary approach helps explain its continuing popularity. A new preface frames the utility of this classic for tomorrow s researchers and businesspeople.