We discuss approaches to the assessment of vulnerability to climate variability and change and attempt to clarify the relationship between the concepts of vulnerability and adaptation. In search of a robust, policy-relevant framework, we define vulnerability in terms of the capacity of individuals and social groups to respond to, that is, to cope with, recover from or adapt to, any external stress placed on their livelihoods and well-being. The approach that we develop places the social and economic well-being of society at the centre of the analysis, focussing on the socio-economic and institutional constraints that limit the capacity to respond. From this perspective, the vulnerability or security of any group is determined by resource availability and by the entitlement of individuals and groups to call on these resources. We illustrate the application of this approach through the results of field research in coastal Vietnam, highlighting shifting patterns of vulnerability to tropical storm impacts at the household- and community-level in response to the current process of economic renovation and drawing conclusions concerning means of supporting the adaptive response to climate stress. Four priorities for action are identified that would improve the situation of the most exposed members of many communities: poverty reduction; risk-spreading through income diversification; respecting common property management rights; and promoting collective security. A sustainable response, we argue, must also address the underlying causes of social vulnerability, including the inequitable distribution of resources.