Concrete structures are able to withstand long-term exposure in the most arduous environments and conditions. But to achieve successful performance, selection of materials, design and construction procedures must be exceptionally well planned and carried out. Extremes of heat and cold, and chemically aggressive environments all make their own particular demands on concrete structures, but the microstructural processes which determine performance have many features in common. This international overview of current research and development contains the papers presented at the First International Conference on Concrete under Severe Conditions, held in Sapporo, Japan, in August 1995.