This chapter examines the ways in which public authorities legitimize and maintain ignorance over long periods of time in the field of environmental health. From an organizational and a comparative international perspective, based on the cases of France and California, the chapter highlights the usefulness of ignorance for the bodies which regulate pesticide occupational hazards. After justifying the need for international comparison to understand the mechanisms that produce ignorance, the chapter suggests that the under-reporting of occupational pesticide poisoning is partly produced by the organizational characteristics of the surveillance programs that are supposed to monitor them. Finally, the chapter reflects on the function that this “organized” ignorance plays in the pesticide regulation systems, arguing that it is a means to solve some of the regulatory inconsistencies underpinning those systems. Policy tools often incorporate implicit views and assumptions on the objects they are supposed to govern.