Chapter 19 What Level Macro? Choosing Appropriate Levels to Assess How Place Influences Population Health Theresa L. Osypuk and Sandro Galea 399 1. Introduction I should venture to assert that the most pervasive fallacy of philosophic thinking goes back to neglect of context. John Dewey Although it has strong historical roots (Davey Smith, Dorling, & Shaw, 2001; Krieger, 2001), the focus on area or contextual causes of health has only recently resurged in epidemiologic studies (Diez Roux, 2001). Most current epidemio- logic inquiry continues to be concerned with studying determinants of health or disease that are proximal to the disease process (compared to causes that are more distal) and causes that are individual-level (compared to those at the population level) (McMichael, 1999). Although higher level causes must be mediated through individual-level and more proximal causes (Diez Roux, 2004b), certain disease causes may not be entirely operationalized at the individual level (Morgenstern, 1985). Increasingly we are recognizing that distal causes manifest- ing at higher spatial levels (e.g., neighborhoods, states) may present greater potential for health prevention than more proximal causes and, as such, are more fundamental causes of health (Link & Phelan, 1996; Schwartz & Diez Roux, 2001). As discussed throughout this book, studying macro-level causes of health and disease above and beyond individual causes may suggest avenues for disease prevention, intervention, and treatment that would not be evident from inquiry restricted to individual-level determinants. Despite our growing appreciation that macro- or higher-levels of causes are fun- damental for population health and health disparities, it is often unclear at what level to conceptualize and operationalize these macro-level causes. This chapter seeks to address this gap. In this chapter, we are concerned with issues pertaining to “macro-level” factors that exist at levels i of spatial aggregation above the indi- vidual and that may pertain to social and physical context as related to health. We begin by discussing historical examples of different spatial levels that have been utilized for examination of health. We next review criteria for choosing what macro level to study, we provide examples of justifications for using various