This study looks into the role of special economic zones in strengthening the competitiveness of economic corridors in the Greater Mekong Subregion (GMS). It examines factors behind the success of special economic zones and the role they can play in GMS economic corridor development. The analysis is based on a company-level survey in the Mae Sot special economic zone and interviews with clients operating in other zones throughout the GMS. The report offers policy recommendations for GMS ministers on how the zones can contribute toward improving competitiveness of economic corridors and thereby promote economic development.