This article offers a social worlds analysis of an emergent and contested scientific paradigm: hormone disruption. It has been argued that humans and wildlife are suffering from health problems resulting from exposure to synthetic chemicals in the environment that mimic natural hormones. Many different social worlds are focused on understanding, expanding, and challenging the concept of hormone disruption, and there is considerable technical and political controversy surrounding this new approach. Using a social worlds analysis, we map the activities of and interactions among some of the communities interested in this paradigm. We pay special attention to the implicated actors involved in—or left out of—the hormone disruptor debates, arguing that it is not enough to ask in the pragmatist sense "who cares" about social phenomena; instead, we must ask "who has the tools and the ability to care" about a certain issue and thus to participate meaningfully in various social worlds.