This study involves a critical review of the current methods used to establish net future physician manpower requirements in Canada. The paper explores specific examples of physician manpower forecasting in Canada, and contrasts them with an extensive U.S. exercise completed recently. The conceptual and measurement difficulties inherent in the Canadian methodology are outlined. Particular attention is paid to the various factors that can potentially influence physician requirements but which are omitted from consideration in traditional forecasting. The paper concludes with a discussion of the definition of 'need' in the context of physician requirements.