Vulnerability is an emerging concept for climate science and policy. Over the past decade, efforts to assess vulnerability to climate change triggered a process of theory development and assessment practice, which is reflected in the reports of the Intergovernmental Panel on Climate Change (IPCC). This paper reviews the historical development of the conceptual ideas underpinning assessments of vulnerability to climate change. We distinguish climate impact assessment, first- and second-generation vulnerability assessment, and adaptation policy assessment. The different generations of assessments are described by means of a conceptual framework that defines key concepts of the assessment and their analytical relationships. The purpose of this conceptual framework is two-fold: first, to present a consistent visual glossary of the main concepts underlying the IPCC approach to vulnerability and its assessment; second, to show the evolution of vulnerability assessments. This evolution is characterized by the progressive inclusion of non-climatic determinants of vulnerability to climate change, including adaptive capacity, and the shift from estimating expected damages to attempting to reduce them. We hope that this paper improves the understanding of the main approaches to climate change vulnerability assessment and their evolution, not only within the climate change community but also among researchers from other scientific communities, who are sometimes puzzled by the unfamiliar use of technical terms in the context of climate change.