During the past century it has been general practice in northern areas to stop most building activities in winter, from the first frost until about the end of March. However, the building trades are becoming more aware that it is often practicable to continue building activities throughout the winter. In order to achieve the proper curing environment for fresh concrete, it is necessary to employ some means of modifying or controlling the effects of weather, regardless of season. Winter concreting poses the special problem of protecting the concrete from the effects of below-freezing temperature until it has attained the necessary "freezing resistance." Electrically heated concrete forms can provide improved protection, and offer a most effective method of curing winter concrete. Electric curing of concrete was first devised in Sweden about forty years ago, and the method was applied to buildings and subway construction in Moscow, Russia. Reports of this work were published in 1932. Nothing further was heard of the system for some years. In 1947 in Hokkaido, Japan, field and laboratory studies were made in electric concrete curing in connection with US Army Camp Crawford at Madamanai. During four years and five winter seasons to the spring of 1951, data was obtained from about 80 structures using some 7,000 cubic yards of plain and reinforced concrete. The results of these tests and field studies revealed many important disclosures, some of which are: (1) that strength can be gained early in ordinary portland cement concrete by means of high temperature curing; (2) warming concrete can be valuable not only in winter, but also in warmer weather, because of the reduction in construction time. The system used employed a network of electrodes, and the heat was generated in the concrete itself by passing alternating current directly into the cement paste.