The purpose of this study is to examine the feasibility of groups of developing countries acting in concert to impose ad valorem taxes on their exports of primary products, with the aim of increasing their net earnings in real terms by improving their terms of trade. Under certain circumstances, such a course of action could increase the welfare not only of developing countries but also of the world. The study also attempts to examine the implications for domestic processing of primary products and incomes stabilization of introducing such a policy.