This paper tries to explain the optimum supply of international public goods and bads between two small open economies, both of which produce two tradable private goods and one non-traded international public good with two kinds of factors the supplies of which are inelastic. Each country can consume domestic and foreign-made public goods by the same amount. Another model deals with international public bads which are good for a providing country but bad for the other country. We show the first-best solution, the optimum tax system, the Nash and Stackelberg equilibria, a free-rider condition and the possibility of immiserizing growth.