Demands for greatly increased power transformer ratings within transport limits which change only slowly have compelled transformer designers to devise new forms of construction which make the best possible use of materials.The paper illustrates this by giving an account of some design problems and some particular solutions. Details are given of a boltless core construction and its effect on noise level. The influence on transformer size and losses of the use of transposed-strip conductor is discussed, and an account is given of a method of calculating disc-winding temperature rise with a digital computer. Stray load losses in the transformer structure can be of considerable magnitude, and methods of reducing them are considered. Some test results are given for core-clamp losses, and a simple method of predicting the effect of magnetic tank shields is described.Finally, a brief account is included of a construction which allows large power transformers to be dismantled for transport and reassembled in such a way that abnormal site testing and processing are avoided.It is concluded that by all such means transformer designers will be able to meet demands for still greater transformer ratings.