In this issue of the Journal, guest editors Daniel Friedman and Barbara Starfield have gathered together and added their voices to an outstanding collection of articles on models for population health. Together, they ask: Do theory and models matter in the conduct of public health research and practice? As researchers involved in community-based public health interventions and programs in Harlem, New York City, our answer is a resounding “yes!” The salience of the population health perspectives presented in this issue is made manifest in relation to 2 of our current projects—namely, evaluation of the Harlem Children’s Zone Asthma Initiative and analysis of the Harlem Household Survey. Both projects were implicitly shaped by what we would now term a population health perspective, in that the health needs of entire communities are embraced and individual, neighborhood, and societal factors are considered important for health and well-being. The theory and models presented in this issue—by explicitly delineating components of population health frameworks and models—can aid such efforts by helping us to conceptualize the pathways through which various factors influence health, thereby suggesting points of intervention and questions to ask when obtaining or analyzing data. The Harlem Children’s Zone Asthma Initiative added a public health component to the longstanding work on school truancy and community-building of the Harlem Children’s Zone, Inc, and the community-based health service delivery efforts of the Department of Pediatrics of Harlem Hospital Center. Building upon a population-based survey of adults in Central Harlem (the Harlem Household Survey), our evaluation perspective was enriched by a history of community-based public health research at the Harlem Health Promotion Center. By embracing a holistic population health perspective, we were able to pull together work with children and with adults, in hospitals and in schools, in our current efforts. This meant shoring up a public hospital center (pediatric ward, emergency department, and clinic) and public school infrastructure with private funding and tailored programs to ensure that the needs of every child in the Harlem Children’s Zone Project are met. One of the things we are learning, according to Dr. Stephen Nicholas, Director of Pediatrics at Harlem Hospital Center, is that coming into people’s homes to deliver interventions helps to remove communication barriers between health care providers and families. In doing so, we hope to improve the health and well-being of all household members—children and adults alike—through home visits for education in medication usage, family-centered primary health care services, and home environmental interventions to remove asthma triggers. The population health perspective does more than encourage these kinds of linkages—it facilitates them. Further, it underscores the need for researchers to use multidisciplinary approaches, to integrate qualitative and quantitative methods, and to recognize the importance of lay knowledge and participatory research (Young TK. Population Health: Concepts and Methods. New York: Oxford University Press Inc; 1998). Steeped in the conduct of community-based research, we can thoughtfully assess which population health models are relevant to our experiences and consistent with our values. Applying population health models—with their emphasis on social processes and conditions—affords an opportunity to test whether interventions that address social inequalities will reduce gaping health disparities across and between populations.