The current paper presents the results of a first global enumeration of slums at the country level. The data are analyzed and comparisons established at sub-regional and regional levels while trying to understand what is happening globally. This document is the culmination of attempts to come to grips with changes in the way we measure slums, starting by providing an agreed universal definition of this type of settlements and a clear methodological approach. The preliminary estimations presented in this document represent a baseline year level that permits the preparation of quantitative estimates for future trends. By providing the methodology and the quantitative knowledge base, the document strives to enhance the use of information on urban poverty, as a powerful policy-making tool to help induce the desired structural changes for poverty alleviation.