Klinger's (1997) ecological theory of policing addresses the intersection of environment and police organizational structure on police patrol practices. It argues that officer actions can be characterized along a continuum of formal authority ranging from vigorous to lenient, where arrest represents more vigor than non-arrest, filing a report more vigor than not filing a report, and so forth. The theory has the potential to explain the spatial patterning of police behavior by incorporating both formal and informal organizational practices and community characteristics. Although the theory has been cited extensively, evaluations have been limited. The single existing direct assessment of Klinger's theory was qualitative, on a small scale, and resulted in findings both consistent with, and in disagreement with, key theoretical postulates (Hassell, 2006). This dissertation is an extensive quantitative examination of this key policing theory, which addresses the following research question; "Is police response to calls for service and self-initiated activity influenced by the level of serious violent crime?" Police responsiveness was measured by the final disposition given to a case and the number of arrests made for low seriousness events; self-initiated activity was measured by the level of traffic enforcement. Additional questions are also addressed such as: Does the relationship between police workload and responsiveness and police workload and self-initiated activity vary over time? If there is a cross-sectional relationship found between these factors, is it contingent upon socio-demographic or land use characteristics of where the events occur? If Klinger's ecological theory of policing is correct it is expected that police will expend less vigor towards low seriousness events and self-initiated activity if there is a great deal of serious crime demanding their attention. The current work also extends the ecological theory in two ways: by expanding and clarifying the impact of environmental factors and by examining the proposed relationship between crime level and vigor within a longitudinal framework. These questions were addressed using data supplied by the Philadelphia Police Department, demographic data from the U.S. Census, and environmental data drawn from a number of sources. Three dependent variables quantified police vigor at different stages of case processing; (1) the number of incidents that resulted in a final disposition of unfounded; (2) the number of low seriousness incidents that ended in an arrest; and (3) the number of traffic stops. These count outcomes were measured at both the census block group level and at the police district level of aggregation. Low seriousness offenses present the greatest opportunities for officer discretion and, therefore, provide officers the most latitude in selecting the vigor of their response. These data were analyzed using both cross-sectional multilevel model (MLM) design and a repeated measure MLM design. Additionally, exploratory spatial data analyses (ESDA) investigated the spatial distributions of these dependent variables. Findings generally support key propositions of Klinger's ecological theory of variations in policing behavior. Vigor varied as a result of officer workload (the number of serious crime incidents) and resource constraint (the number of officer hours assigned to patrol duties). Yet other findings suggested that further conceptual development is still required. The relationship between vigor and key theoretical variables was frequently sensitive to the way vigor was operationalized. More problematically, variations in vigor were expected to be greatest in events of low seriousness. Yet, crime types fall along a continuum of seriousness and imposing arbitrary cut points between low seriousness events and high seriousness events was a difficult task that required either arbitrary distinctions between crime types or value judgments about the seriousness of a crime. Furthermore, these findings suggested that the spatial and temporal resolution through which vigor is investigated will have potentially dramatic impacts upon whether the findings support, or are in contradiction to, key theoretical relationships. These findings, taken a whole, suggest that the ecological theory of policing has strength and utility in explaining patterns of police activity but also that a number of issues could benefit from further conceptual development. / Criminal Justice