This chapter argues that four types of problems can be discerned in the policy process: structured, unstructured, and two types of moderately structured problems. It also argues that policymakers show the inclination to move away from unstructured problems to more structured ones; even at the cost of losing touch with the true complexity and normative volatility of the problems as experienced by other groups. When "containment" efforts fail, problems become unstructured and controversies flare up. This is illustrated in a case study of the so-called "Not In My BackYard"-phenomenon in hazardous waste facility siting. Intractable controversies occur when policymakers stubbornly continue to address the "wrong" policy problem. The chapter shows how these controversies can be transformed into a productive process of learning by problem structuring and problem choice. It discusses political prerequisites for such policy learning and reviews some implications of policy design as well as in policy analysis.