Abstract This paper presents estimates of water requirements for future coal use in the USSR and the U.S. Future levels of coal use were based on scenarios presented by IIASA in Energy in a Finite World. As a first step in the analysis, IIASA's coal scenarios were broken down from the scale of ‘world region’ to the scale of coal-producing region. This exercise revealed that American and Soviet coal targets, which seem feasible when viewed on the ‘world-region’ scale, may be difficult to attain on the coal-region scale due to insufficient coal reserves in some regions. In the next stage of the analysis, an analytical model was developed, which describes on the coal-region scale the quantity of water required during different stages of coal development from mining to its final conversion to useful energy. Application of this model to each of ten principal coal-producing regions of the US and USSR suggested that roughly 1–2 tons of water will be consumed for every ton-equivalent (tce) of coal-fuel delivered. However, these estimates assume a high degree of water conservation; with less emphasis on conservation, perhaps 50% more water will be required. Water requirements for coal were then compared with competitive water uses in each U.S. coal region, as well as estimates of surface water supply in these regions. It was found that the amount of water needed for coal is small relative to other projected water uses such as agriculture and industry. However, after accounting for competitive water uses, there will probably be little or no water available for coal use during dry years in the Southwest and Northwest regions. Unless significant quantities of water can be stored for these years, coal development will have to displace other water uses in these regions. Intense water pressure will probably also occur in the Asian-USSR coal region of Ekibastuz, and possibly in Kuznetsk, Kansk-Achinsk, and Tungusska. It is concluded, therefore, that an overall four- or fivefold expansion of coal use in the U.S. and Soviet Union will probably be constrained to some degree by both limited coal reserves and lack of readily available water.