The Vulnerability Sourcebook provides step-by-step guidelines to conduct vulnerability assessments and to monitor changes in vulnerability over time. Repeating vulnerability assessments on a regular basis is a rather new approach and serves as a valuable tool for monitoring and evaluating the effectiveness of adaptation by showing whether a reduction in vulnerability has really been achieved. The Vulnerability Sourcebook is structured along eight modules which provide detailed guidance on the operationalisation of a vulnerability assessment. A key element is the development ofclimate change impact chains building on the approach developed by Germany’s ‘Vulnerability Network’ for assessing domestic vulnerability across different sectors at the various administrative levels in Germany. The approach of the Sourcebook is applicable from national to local level and to a broad range of sectors. It is illustrated with examples and lessons learned from pilot applications in Bolivia, Pakistan, Burundi and Mozambique.