Most of the upland areas of Southeast Asia are characterized by insufficient infrastructure, low productivity in smallholder crop and animal production, mounting environmental problems such as soil and forest degradation and loss of biodiversity, increasing population pressure, and widespread poverty, particular in rural areas. While some upland areas in South East Asia have been experiencing considerable progress during the past twenty years, others have stagnated or even declined with respect to economic, social and environmental objectives of development. The purpose of the paper is to describe major trends regarding sustainable development in the upland areas of selected countries in South East Asia, and review explanatory approaches for the observed trends based on case studies from Cambodia, Laos, Thailand, Vietnam, and Indonesia. The conceptual framework for this paper builds on the critical triangle of sustainable rural development. Here, equity or poverty alleviation, economic growth, and the protection of the environment are the three major policy objectives. We further distinguish three explanatory approaches for land use change and agricultural and rural development. Apart from the market approach and the population approach, we suggest that future studies should focus more on governance issues as a major driving force of land use change. The governance approach appears particularly relevant for upland areas which are often politically and institutionally marginalized. The paper begins with a review of definitions of sustainability, and proceeds with a conceptual analysis of the two-way linkages between poverty and the environment, and poverty and economic growth in rural areas. This is followed by empirical findings from research on agriculture and forestry as the major land uses in upland areas of selected South East Asian countries. Based on the results of different case studies from Cambodia, Laos, Vietnam and Indonesia, we seek to contrast stories of relative success with those of failure. The paper concludes with implications for rural and agricultural development policies, and suggests future areas of research.