The Greater Mekong Subregion (GMS) is one of the fastest developing regions in the world, experiencing significant economic, environmental and social transformations. There is an increasing demand for policy relevant and decision support information at micro level. This PhD research contributes to the emerging body of knowledge through quantitative investigation of: (i) rural household incomes, livelihood strategies and dynamics; (ii) micro-level vulnerability to climate and land use change; and (iii) adaptation decision-making processes. This research project was primarily carried out in Cambodia and Laos, two of the poorest countries in the GMS. Structured household surveys and participatory focus group discussions were the primary data collection methods. The findings provide new, additional and much needed quantitative information in the region, and several policy implications for rural development and adaptation planning in the local context and broadly in low-income countries.