An important purpose of trade taxes in developing countries is the raising of revenue with which to finance development expenditures. Indeed, for countries in the earliest years of economic development, taxes on foreign trade, because of their greater ease of collection when compared with indirect and, particularly, direct domestic taxes, are a major source of government revenue. According to a study of Chelliah et al. (1975), the contribution of trade taxes to total tax revenue in 46 LDCs in 1969-71 averaged 32-2 per cent, with contributions ranging as high as Zaire's 65 5 per cent. These taxes can be either explicit import duties or export taxes, or implicit equivalents, such as auctioned import quotas, differential exchange rates or the pricing policies of marketing boards with statutory monopolies of export crops.' It would plainly be of interest to know the welfare cost to a developing country of using trade restrictions as revenue-raising devices. In the case of a country with negligible monopoly/monopsony power in world markets, probably not an inaccurate description of many LDCs, an explicit measure of the cost of trade taxes has been developed by Johnson (1960), the measure involving both income and (own and cross-) price elasticities of demand and (own and cross-) price elasticities of supply of traded goods. Because application of the measure... to an actual economy would obviously require a major statistical (Johnson, 1960, p. 335), Johnson's subsequent work (1965) limited attention to the cost of trade taxes in hypothetical two-good economies, in which community preferences and production possibilities were simply assumed to have particular functional forms. In the context of the least developed countries, however, an alternative, not obviously more drastic, means of lessening the required statistical effort suggests itself. Rather than arbitrarily attributing specific forms to technology and preferences, one might instead attribute a specific objective to government in its design of the trade tax structure, namely the maximization of revenue. Should that be a reasonable approximation to the structure's purpose, then a calculation of Johnson's measure of the associated welfare cost is shown in this paper to require estimates only of total revenue from taxes on foreign trade, world prices and marginal propensities to consume. No knowledge of price elasticities of demand or supply is required, a considerable informational economy. Indeed, the measure of loss assumes a particularly simple form, the product of a half trade tax revenue and the world-price-weighted sum of income derivatives of demand for traded goods. A developing country's trade tax structure may, however, reflect a compromise between the objectives of raising tax revenue and of increasing self-sufficiency, objectives that are in conflict whenever the desired degree of self-sufficiency exceeds that obtained under maximum revenue trade taxes.