The preparation of large single crystals of silicon-iron in sheet form by the strain-anneal method is described in detail. Whole-sheet single crystals up to 2¾ in wide and 21 in long, and having a crystallographic plane either of the form {100} or {110} in the plane of the sheet, have been made successfully from 2% silicon commercial electrical sheet using Dunn's method. Certain limitations in the orientations it was possible to produce by this means were observed with the materials used, attempts to grow crystals having a {1ll} in their plane, for example, being unsuccessful. The many factors affecting recrystallization are discussed. Carbon contents of the order of 0.015% were observed in several of the crystals prepared.One of the crystals with a silicon content of 2.11% exhibited no phase change up to a temperature of 1 140°C, i.e. 40–50°C above the temperature at which it was grown, and examination by X-rays showed it to be of exceedingly high quality with an estimated range of misorientation of not more than ten minutes of arc.A magnetic torque curve for a 1¼-in diameter single-crystal disc having a {100} cube face in its plane is given, and the magnetization curve in the {100} direction for a “picture-frame” sample of external dimensions 1⅞-in square is also included. The former shows that it is more accurate to take a figure of 89% of the unique infinite field value of the anisotropic constant K1when analysing torque curves obtained on 0.014-in thick discs of 1¼-in diameter in applied fields of the order of 2 000 oersteds, and this figure is in good agreement with the correction suggested by Tarasov.