This paper aims to assess the role of instabilities on Africa's low rates of growth during the seventies and eighties, using cross-section econometric estimates, on a sample of African and non-African countries and two pooled decades. Africa exhibits higher 'primary' instabilities (climatic, terms of trade and political instabilities), i.e., instabilities which are structural rather than the result of policy. These 'primary' instabilities influence African growth more through a lower growth residual than through a lower average rate of investment. They do so by their impact on economic policy, which is evidenced by their influence on two 'intermediate' instabilities, the instabilities of the rate of investment and of the real exchange rate, which significantly lower the rate of growth.