The purpose of this study is to provide better scientific information about the effects of intra-urban population distribution on several social, psychological, and somatic pathologies. It is to produce additional research on the "density-pathology" relationship at the ecological level. We plan to study four cities or metropolitan areas of different sizes and types of population distribution. In each we will examine the distribution in relationship to a variety of pathologies, such as crime, delinquency, infant mortality, and others. We introduce three departures from the methods of studies currently available: (1) We examine distribution through the method of population potential as well as density. (2) We use the block as the unit of analysis. (3) We examine a more extensive and more refined set of pathologies. Population distribution is the one element of population which is directly regulated in the United States. The regulations include zoning regulations, building regulations, regional plans, and several indirect methods. As such it is an important and neglected topic of demographic policy-oriented research.