The Greater Mekong Subregion (GMS) comprises Cambodia, the People's Republic of China, Lao People's Democratic Republic, Myanmar, Thailand, and Viet Nam.

In 1992, with ADB's assistance, the six countries entered into a program of subregional economic cooperation, designed to enhance economic relations among the countries.

The GMS Program, with support from ADB and other donors, helps the implementation of high priority subregional projects in transport, energy, telecommunications, environment, human resource development, tourism, trade, private sector investment, and agriculture.

Substantial progress has been achieved in terms of implementing GMS projects since 1992. Priority infrastructure projects worth around US$10 billion have either been completed or are being implemented. Among these are the upgrading of the Phnom Penh (Cambodia)-Ho Chi Minh City (Viet Nam) highway and the East-West Economic Corridor that will eventually extend from the Andaman Sea to Da Nang.