In South Africa, as in much of the developing world, youth participation in the informal, unregulated street pesticide market results in exposures and risks of acute and chronic effects, yet has gone largely undocumented. A conceptual framework for understanding youth involvement in street pesticide sales and use includes contextual factors, health outcomes, and externalities (unintended negative consequences). An exploratory study based on this framework shows that highly-toxic pesticides, such as aldicarb, methamidophos, and chlorpyrifos, are easily available in informal markets in Cape Town's urban periphery. Youth are involved in the sale, distribution, and use of street pesticides, and are exposed during handling, transportation, spillage, storage, use and other activities, with little safety information available. Demand and supply for street pesticides is driven by joblessness, poverty, and inadequate pest management strategies. National and international efforts addressing underlying contextual determinants are required to protect children from exposures to street pesticides.