Critical deficiency maps, conceived as objective, uniformly applicable technical tools that could be employed to make social expenditure more efficient and effective, constitute the most ambitious and successful method devised to date for using census data for social planning in Latin America and the Caribbean. Nevertheless, while their importance and potential as a policy tool have gained increasing recognition, questions have arisen concerning their virtues and limitations and on how they could be made to serve the need for more complex social information or to reveal the changing forms that poverty assumes. This article addresses five of the questions most frequently posed about the maps: How accurately do they identify or exclude beneficiaries of anti-poverty programmes? How well do they handle comparisons over time? How well do they handle spatial comparisons? How easily can they incorporate updated information? And how appropriate are the research variables chosen?