Recent papers by Néel (8) and Lawton and Stewart (7) have provided an explanation of the process of magnetization in a single crystal, using the well-known ideas of the domain theory but bringing out the important role played by the demagnetizing field. These authors applied their ideas to two shapes of single crystals of iron, long rods and oblate spheroids, but in the latter case the only crystal orientation worked out in detail was that in which the equatorial plane was (100). The case of oblate spheroids of iron and iron-silicon where the equatorial plane is a (110) plane of the crystal, and the magnetic field is applied in this plane, are considered in detail in this paper. Calculations are made for In, the component of magnetization perpendicular to the applied field He, and comparison made with experimental measurements. This particular problem was considered by Bozorth and Williams (4) who calculated the torque per unit volume (i.e. the product InHe) experienced by the crystal in a magnetic field. Their calculations are, however, incomplete, because their picture of the magnetization process is not a valid one in moderate fields. Moreover, the demagnetizing field was taken into account only in assessing the size of the field H acting within the crystal, but not its direction.