This paper reviews the state of knowledge on social vulnerability to climate change in three hot spots (deltas, semi-arid regions and snowpack-or glacier-fed river basins) in Africa, Central Asia and South Asia, using elements of systematic review methods. Social vulnerability is defined as a dynamic state of societies comprising exposure, sensitivity and adaptive capacity. We examine whether the hot spots have specific characteristics that tend to increase or decrease social vulnerability, consider suitable scales of analysis for understanding vulnerability, and explore the conceptions of vulnerability adopted in the climate change literature and the nature of the insights this generates. Finally, we identify knowledge gaps in this literature. All three hot spots are characterized by high levels of natural resource dependence, with increasing environmental degradation. They also exhibit unequal policies and patterns of development, which benefit certain segments of society while making others more vulnerable. Vulnerability is driven by multiple factors operating at different scales; however, characterization of cross-scalar interactions is poorly developed in the majority of studies reviewed. Most studies are either large scale, such as broad comparisons of vulnerability across countries, or local, documenting community-level processes. Detailed understanding of the interactions between climate change impacts on natural systems, and socio-economic trajectories, including adaptation, also emerges as a knowledge gap.