Abstract There has been an increase in interest towards corporate activities aimed at reducing or eliminating the waste created during the production, use and/or disposal of the firm’s products. Prior research has focused on the need for such activities, while current research tries to identify those components that encourage or discourage such activities. As a result of the introduction of ISO 14001, attention has turned to corporate environmental management systems (EMS). The underlying assumption is that such a system is critical to a firm’s ability to reduce waste and pollution while simultaneously improving overall performance. This study evaluates this assumption. Drawing on data provided by a survey of North American managers, their attitudes toward EMS and ISO 14001, this study assesses the relative effects of having a formal but uncertified EMS compared to having a formal, certified system. The results strongly demonstrate that firms in possession of a formal EMS perceive impacts well beyond pollution abatement and see a critical positive impact on many dimensions of operations performance. The results also show that firms having gone through EMS certification experience a greater impact on performance than do firms that have not certified their EMS. Additionally, experience with these systems over time has a greater impact on the selection and use of environmental options. These results demonstrate the need for further investigation into EMS, the environmental options a firm chooses, and the direct and indirect relationships between these systems and performance.