Poverty alleviation efforts are best founded on a sound diagnosis of the underlying causes and dimensions of poverty. Across different countries, regions, communities or even families, the identity of the poor, the degree of their poverty and its causes, will differ. In order to develop realistic policies for poverty alleviation in a given setting, it is essential to understand the nature of poverty in that specific setting. This study explores types of poverty lines, alternate approaches to setting poverty lines, issues arising from the constructions of poverty lines and methods for testing the robustness of poverty comparisons. The paper was delivered at the Asia and Pacific Forum on Poverty: Reforming Policies and Institutions for Poverty Reduction, held at the Asian Development Bank in Manila in 2001.