The population ecology perspective on organization-environment relations is proposed as an alternative to the dominant adaptation perspective. The strength of inertial pressures on organizational structure suggests the application of models that depend on competition and selection in populations of organizations. Several such models as well as issues that arise in attempts to apply them to the organization-environment problem are discussed. The paper suggests a reformulation of the problem in terms of population ecology. While there is a wide variety of ecological perspectives, all give emphasis to selection. That is, they attribute patterns in nature to the action of selection processes. The vast literature on organizations contributes to a different view, which we call the adaptation perspective. According to this perspective, subunits of an organization—usually coalitions of managers or dominant coalitions—scan the relevant environment for opportunities and threats, formulate strategic responses, and adjust the organizational structure appropriately. The adaptation perspective is more clearly seen in the literature on management. Contributors of this assume, generally, a hierarchy of authority and control that determines decisions regarding the organization as a whole at the top. Then, organizations are affected by their environments according to the ways in which managers or leaders formulate strategies, make decisions, and implement them. Particularly successful managers are capable of both safeguarding their organizations from environmental disturbances and organizing minor adjustments that require minimal structural disturbance. A similar perspective, often expressed differently, dominates the sociological literature on the subject. It plays an important role in the functional analysis of the relationship between the organization and the environment by Parsons (1956) and is found in a more strictly Weberian tradition (see Selznick, 1957). It is interesting to note that while functionalists have been interested in the effects of the system and base much of their approach on the logic of survival imperatives, they have not dealt with selection phenomena. That is, probably a reaction against the theory of organization that reflects social Darwinism. Supporters of exchange theory also adopted the adaptation perspective (Levine and White, 1961), and it is natural that theories emphasizing decision-making tend to adopt the adaptation view (March and Simon, 1958; Cyert and March, 1963). Even the celebrated synthesis of Thompson (1967) between open and closed systems thinking addresses the adaptation perspective explicitly (see, particularly, the second part of Thompson's book). Clearly, the leaders of organizations really formulate strategies and organizations adapt to environmental contingencies. As a result, at least some relationship between structure and environment must reflect adaptive behavior or learning. However, there is no reason to conclude that the large structural variability of organizations reflects only or deterministically an adaptation. There are many limitations in the adaptability of organizations, that is, there are many processes that generate structural inertia. The stronger the pressures, the less the adaptability of organizations and the more likely that the logic of environmental selection is appropriate. As a consequence, the problem of structural inertia isThe population ecology perspective on organization-environment relations is proposed as an alternative to the dominant adaptation perspective. The strength of inertial pressures on organizational structure suggests the application of models that depend on competition and selection in populations of organizations. Several such models as well as issues that arise in attempts to apply them to the organization-environment problem are discussed. The paper suggests a reformulation of the problem in terms of population ecology. While there is a wide variety of ecological perspectives, all give emphasis to selection. That is, they attribute patterns in nature to the action of selection processes. The vast literature on organizations contributes to a different view, which we call the adaptation perspective. According to this perspective, subunits of an organization—usually coalitions of managers or dominant coalitions—scan the relevant environment for opportunities and threats, formulate strategic responses, and adjust the organizational structure appropriately. The adaptation perspective is more clearly seen in the literature on management. Contributors of this assume, generally, a hierarchy of authority and control that determines decisions regarding the organization as a whole at the top. Then, organizations are affected by their environments according to the ways in which managers or leaders formulate strategies, make decisions, and implement them. Particularly successful managers are capable of both safeguarding their organizations from environmental disturbances and organizing minor adjustments that require minimal structural disturbance. A similar perspective, often expressed differently, dominates the sociological literature on the subject. It plays an important role in the functional analysis of the relationship between the organization and the environment by Parsons (1956) and is found in a more strictly Weberian tradition (see Selznick, 1957). It is interesting to note that while functionalists have been interested in the effects of the system and base much of their approach on the logic of survival imperatives, they have not dealt with selection phenomena. That is, probably a reaction against the theory of organization that reflects social Darwinism. Supporters of exchange theory also adopted the adaptation perspective (Levine and White, 1961), and it is natural that theories emphasizing decision-making tend to adopt the adaptation view (March and Simon, 1958; Cyert and March, 1963). Even the celebrated synthesis of Thompson (1967) between open and closed systems thinking addresses the adaptation perspective explicitly (see, particularly, the second part of Thompson's book). Clearly, the leaders of organizations really formulate strategies and organizations adapt to environmental contingencies. As a result, at least some relationship between structure and environment must reflect adaptive behavior or learning. However, there is no reason to conclude that the large structural variability of organizations reflects only or deterministically an adaptation. There are many limitations in the adaptability of organizations, that is, there are many processes that generate structural inertia. The stronger the pressures, the less the adaptability of organizations and the more likely that the logic of environmental selection is appropriate. As a consequence, the problem of structural inertia is