It has been suggested in the past that agricultural economists have had a limited input to the agricultural policy making process because of their preoccupation with issues of economic efficiency. The contrary hypothesis that the contribution of agricultural economists to the policy debate is hampered as much by our limited understanding of human behaviour and the lack of relevant data as it is by any preoccupation with efficiency is advanced in this paper. This notion is illustrated with reference to commodity stabilisation policy, the role of expectations in economic models, the economics of regulation and issues associated with the competitiveness of the rural sector. In discussing these issues, an attempt is made to outline areas where research is needed in order that agricultural economists can further the policy debate.