During the past decade world coal consumption has expanded by about 26% whilst energy demands overall have grown by only 17%. This is because of the increased price of oil products, plus a period during which the costs of mining coal in many parts of the world have been moderately well contained. Over-ambitious forecasts of coal demand have encouraged the considerable over-investment in coalmining capacity that exists today. Costs of winning coal and transporting it are low, but sales depend on the rate of growth of a country's demand for energy. Some countries are more successful at marketing coal than others. Amongst the major factors that influence the rate of substitution of one source of energy for another is the nature and age of the boiler stock. The outcome of the developing environmental debate and calls for reduction in SO/sub 2/ and NO/sub x/ emissions from coal-fired boilers is going to affect coal's fortunes in the 1990's.