This article provides an overview of the ways in which mass communication has been used -- or can be used -- to promote beneficial changes in behavior among members of populations. We use an ecological perspective to examine the ways in which mass media interventions can be used to influence public behavior both directly and indirectly. Mass media interventions that seek to influence people directly -- by directly targeting the people burdened by the public health problem of concern and/or the people who influence them -- have a long basis in public health history, and recent reviews have clarified our expectations about what can be expected from such approaches. Mass media interventions that seek to influence people indirectly -- by creating beneficial changes in the places (or environments) in which people live and work -- have equal if not greater potential to promote beneficial changes in population health behaviors, but these are currently less explored options. To have the greatest possible beneficial influence on public behavior with the public health resources available, we recommend that public health program planners assess their opportunities to use media to target both people and places in a manner that complements and extends other investments being made in population health enhancement.