Governments often operate under considerable pressure to respond effectively to the emergence of increasingly complex policy dilemmas. This article first explains some key difficulties in bringing forth comprehensive policy interventions. Despite the ubiquity of social and political constraints to policy innovation, many failures can be attributed to public bureaucracies that are not designed to deal with complex problems, and which all too quickly exceed their policy-making capacities. This study then analyzes why comprehensive policy-making does sometimes occur, and links its occurrence to bureaucratic design factors, arguing that extending organizational capacity for innovation involves more than generous budgets and expertise. The article draws upon, and develops further, Mintzberg's ideas on administrative adhocracy to show how administrative units can be organized to enable bureaucracies to transcend professional compartmentalization and routine; and how structures can be designed for comprehensive policy innovation. The study focuses on Canadian federal bureaucracy, and it is supported by three case studies of recent policy experiments: energy, environment and AIDS.