Canada's House of Commons committee system, established to enhance the effectiveness of parliament, has operated in approximately its present form since 1986. However, information about what it accomplishes remains limited. This article focuses on the investigative/policy studies of committees. A questionnaire given to former cabinet ministers and analysis of previously unexplored committee data support the view that these studies have achieved a modest influence on governments, well short of expectations held in the mid-1980s. Furthermore, their influence is as a source of political intelligence more than the collaborative policy work and technical expertise given central importance by creators of the system. This supports scepticism about the influence achieved by the all-party agreement that continues to be reflected in about 70 per cent of committee reports, and may also be reflected in the written responses to committee reports by governments, an estimated 50 per cent of which are ambiguous. Nevertheless, the original vision reflected in the committees persists among many Canadian advocates of parliamentary reform.