The principal soft ferromagnetic materials in use today are still iron and silicon-iron alloys. Factors affecting magnetic properties of importance in practical use are evaluated and related to properties attainable in iron and electrical steels. Developments in metallurgy and technology leading up to the present status of com-merical materials in the principal categories of iron, low-carbon steel, nonoriented silicon-iron and grain-oriented silicon-iron are described. Improvements in magnetic properties have been achieved primarily by minimizing chemical impurities and controlling crystal orientation. The relation of material properties to applications is discussed and an evaluation of possible future developments is made.