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The fuel costs and the impacts of energy use on the local environment make it necessary to reduce the consumption of energy of industrial processes. The use of waste heat recovery technologies is an effective way of achieving energy saving and therefore a reduction in energy consumption. In order to assess accurately the potential of waste heat recovery, it is necessary to know in detail the characteristics of the process streams. It is also necessary to examine in depth the different recovery technologies, to be able to integrate the set: waste heat-recovery technology-useful flow. Using the Basque Country industrial database and thermodynamic properties databases, the energy and exergy of waste heat have been determined for 10 industrial sectors of the Basque Country. The sectors have been classified according to their type into gases, liquid effluents and solid product streams, and also according to the temperature levels associated with them. In accordance with available data, energy content of waste heats amounts to 40% of total energy consumption in the industrial sectors of the Basque Country. Making a breakdown for types, we found that 33% of the energy of waste heat appears in the gas streams from combustion equipment, 27% is sensible heat of solid products, 16% is vapour, 11% liquid effluents and the rest appears as radiation, gases or by-products. More than half of this energy content appears at temperatures higher than 523 K. © 1997 Published by Elsevier Science Ltd.