How are environmental provisions incorporated in regional trade agreements (RTAs)? What are the environmental impacts of RTAs? How can RTAs contribute to green growth? These questions were discussed at the fourth OECD Workshop on Regional Trade Agreements and the Environment, held by the OECD Joint Working Party on Trade and Environment (JWPTE) in Paris on 1-2 June 2010. Participants included JWPTE delegates and other representatives from OECD members and other countries, and representatives from intergovernmental organisations, non-governmental organisations and academia. Participants discussed characteristics of RTAs, free trade agreements and other trade arrangements, including co-operation activities and capacity building, public participation, consultation mechanisms and dispute settlement. The workshop also reviewed experiences in assessing the environmental impacts of such agreements, looking at ex ante as well as ex post evaluations. This document presents the main outcomes of the workshop.