This paper attempts a comprehensive accounting of climate change vulnerability for 233 states, ranging in size from China to Tokelau. Using the most recent evidence, it develops risk indicators for three critical problems: increasing weather-related disasters, sea-level rise, and loss of agricultural productivity. The paper embeds these indicators in a methodology for cost-effective allocation of adaptation assistance. The methodology can be applied easily and consistently to all 233 states and all three problems, or to any subset that may be of interest to particular donors. Institutional perspectives and priorities differ; the paper develops resource allocation formulas for three cases: potential climate impacts alone, as measured by the three indicators; case 1 adjusted for differential country vulnerability, which is affected by economic development and governance; and case 2 adjusted for donor concerns related to project economics: intercountry differences in project unit costs and probabilities of project success. The paper is accompanied by an Excel database with complete data for all 233 countries. It provides two illustrative applications of the database and methodology: assistance for adaptation to sea level rise by the 20 island states that are both small and poor and general assistance to all low-income countries for adaptation to extreme weather changes, sea-level rise, and agricultural productivity loss.