Analysis of the role of structural change in labor movement revitalization is presented as part of a multicountry comparative project. There are two interrelated causal chains that explain successful union restructuring. First, there must be sufficient environmental pressure to overcome institutional inertia. Second, unions J need a clearly articulated vision that provides a basis for strategic decision making. Three viable motivations for restructuring are identified: aggressive, defensive, and strategic. Aggressive restructuring strengthens union leadership; defensive restructuring attempts to stabilize the union to assure survival. If the restructuring is merely aggressive or merely defensive, however, it will not contribute to a net increase in membership or power. Strategic restructuring involves substantial organizational change and promises to augment union power and contribute to renewal. This conceptual framework is presented in the context of comparative analysis designed to assess whether restructuring is essential for union revitalization.