Beginning in the late 1990s, Canada and the United States began requiring "Environmental Reviews (ERs)" of all trade agreements to be negotiated by each government. This paper, commissioned by the North American Commission for Environmental Cooperation, outlines how ERs have evolved in North America, and evaluates the different methodological approaches that have been employed in ERs thus far. We show that the ERs conducted to date have an encouraging number of strengths that can be built upon. However, we also establish that the art of conducting ERs is still in its infancy. We identify four limitations with the methodological approaches that have been employed in the most recent ERs. Based on an analysis of these limitations, we propose four ways to improve how ERs are conducted in the future.