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Tax collection depends in large part on a system for motivating officiais with responsibility for collecting taxes. In Sub-Saharan Africa, a strong asymmetry of access to information between government and tax collection agents explains why the government is often reduced to negotiating with the agents in order to establish a set amount of taxes to be paid to the Treasury. As a resuit, previsions of tax revenues by treasury officiais are not necessarily any worse than those obtained by using sophisticated macrœconomic methods. This also explains why the reforms introduced in structural adjustment programmes have not succeeded in producing a significant and sustained increase in the rates of tax gathering. These reforms have mainly affected the fiscal arrangements as such without giving sufficient weight to the motivation system of the fiscal and customs services.