Many researchers hope to see the best available research evidence used in policy-making to address important public problems. However, policy often appears to be based on anything but the research evidence, as the problem of conduct disorder (or severe antisocial behaviour in children) shows. In Canada, few children receive effective prevention or treatment programs, and incarceration is overused, despite evidence that it is ineffective and potentially harmful. Using the example of conduct disorder, we investigated why policy-making has not reflected the research evidence, examining research use in the context of competing influences on the policy process. Qualitative methods were used to analyze data from interviews with thirty-two politicians and senior civil servants. Our allegiance to rationality wavered as we listened to policy-makers who contended with the inherent ambiguity in the policy process. They told us that they managed institutional constraints including fragmentation across levels and sectors of government, and the long-term effects of fiscal restraint. They also reconciled the competing interests of stakeholders' priorities, the public's response to negative events involving children and the media's role in shaping this response. Ideas about youth violence were morally charged, but policy-makers remained committed to improving children's lives. Day-to-day, policy-makers obtained most of their information internally and informally. Research evidence was valued and used, but as just one source of ideas and information among many. In this environment of ambiguity, creative civil servants formed partnerships with trusted researchers in order to change policy. Our findings suggest that the use of research evidence in policy-making could be enhanced if researchers learned about the competing influences on the policy process, formed research-policy partnerships, challenged the incentives within research institutions, and engaged in public debates about important problems, such as child antisocial behaviour.