The review paper traces the history of superconductivity from its discovery in 1911 to the more recent developments of superconductors that are potentially useful in practical applications. The present state of knowledge of the theory of superconduction is presented in sufficient detail to gain an understanding of the phenomenon and the characteristics that will be important to the engineer. This leads to a summary of the exploitable properties of superconductors. The need for a low-temperature environment itself brings technological problems and the need for auxiliary equipment of reliability higher than at present exists, and hence the evolution of specialised design practices and solutions. The state of development of a range of actual and potential applications of superconductors is assessed in terms of research magnets, electrical machines, cables, transformers, magnetic suspension, energy storage and others. The authors conclude that, while the range of applications likely to be realised in commercial practice is perhaps less than that being advocated a few years ago, certain areas of development of large-scale electrical-engineering equipment employing superconductors will attract increasing interest and effort in the future.