Many corporations now recognize the importance of establishing a "proactive" environmental strategy. This article develops a framework for environmental strategy implementation based on case studies of three firms: Volvo, Polaroid, and Proctor & Gamble. The degree to which each firm's environmental strategy focuses on market or nonmarket areas reflects its existing core competencies. Effective implementation of this strategy often requires new environmental management systems, which need to be designed in ways that remove organizational buffers and integrate well with existing core activities. However, while tailoring programs to fit existing activities is useful in the initial stages of implementation, it sometimes creates its own set of problems as environmental programs mature.