Asthma is not equally distributed across regions, populations, or communities. This original research examines the spatial distribution of Central Harlem residents visiting the local Emergency Department for asthma treatment. Using geographic information systems to create new spatially-defined areas for analysis, the ecological study shows how archival data can be used to identify "hot-spots" or clusters of asthma emergency cases. It tests the hypothesis that the spatial distribution of patients' residential addresses can be explained through analysis of environmental factors affecting neighborhood and housing quality. Multilevel analysis offers a methodological approach that enhances the validity of applying aggregated data to explain the individual level outcomes. The findings offer evidence for the role of underlying community environmental factors in asthma emergency and insights into areas for intervention. "A genuine and realistic examination of asthma and neighborhood environments." PC Lippman, JCJ Architecture