At the broadest level this is an investigation of the structural antecedents and behavior consequences of interpersonal networks. We are particularly interested in the ethnic character of interpersonal networks. Networks are viewed as the mechanisms linking individuals to the institutional structure of the city. The character of interpersonal networks reflect the structural position of individuals and groups. They also appear to have an impact on a series of variables including ethnic salience, occupational mobility, residential stability, neighborhood satisfaction and family structure. The research consists of two interrelated components. In cooperation with the Philadelphia Social History Project we are tracing the relationship between the economic structure of the city, the position of groups in the city's division of labor, and the location, stability, and character of local areas between 1850 and 1970. The historical analyses provides the structural context for a more detailed investigation of the characteristics of contemporary neighborhoods and communities. A sample survey (1,780 respondents who are representative of the metropolitan area) enables us to link the position of groups in the structure of the city to the character of interpersonal networks and ultimately to individual behavior patterns.