This evaluation is one of five thematic evaluations undertaken by the Tsunami Evaluation Coalition (TEC) on the international humanitarian response to the tsunami. The other four in the series cover: coordination; the impact of the response on local and national capacities; linkages between relief, rehabilitation and development; and the funding response to the tsunami. This report evaluates the adequacy, appropriateness and effectiveness of the assessment of need in the first three months after the tsunami. It focuses on the impact of assessment on the response of international agencies and institutional donors and, ultimately, on the affected populations.