Growers and the USDA showed increasing favor for agricultural chemicals over cultural and biological forms of pest control through the first half of the twentieth century. With the introduction of DDT and other synthetic chemicals to commercial markets in the post-World War II era, pesticides became entrenched as the primary form of pest control in the industrial agriculture production system. Despite accumulating evidence that some pesticides posed a threat to human and environmental health, growers and government exercised path-dependent behavior in the development and implementation of pest control strategies. As pests developed resistance to regimens of agricultural chemicals, growers applied pesticides with greater toxicity in higher volumes to their fields with little consideration for the unintended consequences of using the economic poisons. Consequently, pressure from non-governmental organizations proved a necessary predicate for pesticide reform. This dissertation uses a series of case studies to examine the role of non-governmental organizations, particularly environmental organizations and farmworker groups, in pesticide reform from 1962 to 2011. For nearly fifty years, these groups served as educators, communicating scientific and experiential information about the adverse effects of pesticides on human health and environment to the public, and built support for the amendment of pesticide policies and the alteration of pesticide use practices. Their efforts led to the passage of more stringent regulations to better protect farmworkers, the public, and the environment. Environmental organizations and farmworker groups also acted as watchdogs, monitoring the activity of regulatory agencies and bringing suit when necessary to ensure that they fulfilled their responsibilities to the public. This dissertation will build on previous scholarly work to show increasing collaboration between farmworker groups and environmental organizations. It argues that the organizations shared a common concern about the effects of pesticides on human health, which enabled bridge-builders within the disparate organizations to foster cooperative relationships. Bridge-building proved a mutually beneficial exercise. Variance in organizational strategies and the timing of different reform efforts limited, but did not eliminate, opportunities for collaboration. Coalitions formed when groups came together temporarily, and then drifted apart when a reform effort reached its terminus, leaving future collaboration still possible.