We propose to study the relationship between population density and human behavior in a large urban area--Chicago. The study will examine the relationships between varying levels of density and a number of rates of "pathological" behavior at the ecological or areal level, and try to establish the relative importance of density as an explanatory variable when compared to other more traditional sociological variables such as race and social class. The study will then proceed from these ecological findings to a detailed analysis of individual households, through the use of a structured interview, administered to a representative sample of persons stratified by density, social class, and levels of "pathological" behavior, such as morbidity, fertility, ineffectual child care, antisocial behavior, and psychiatric disorder. Our goal is to not only establish whether there is a relationship between high density and specific types of behavior, but to also try to determine the specific nature of these relationships. The supplemental funds for which we are now applying will be used to enrich the original research through three related sub-projects. First, we expand the ecological analysis in time (1940 through 1970, instead of focusing on 1970 only) and geographical scope (covering 198 large cities in the United States, instead of only Chicago). Second, we examine the patterns of housing segregation, crowding, and family stability for the Puerto Rican population of Chicago. Third, we examine fertility differentials among European ethnic groups in the United States.