The dependence of magnetization M on field H has been measured in high fields (15-150 kOe) for single crystals of Ni and Fe+4% Si in their directions of easy magnetization. The specimen, at liquid-nitrogen or liquid-helium temperature, was pulled from one to the other of two balanced coils connected in a series opposition to an integrating digital voltmeter. Over the range 15 to 50 kOe, where the most accurate data were obtained, the mean volume susceptibility κ=∂M/∂H is a little over 0.5×10 -4 emu/cm3 for Ni, 1.1×10-4 for Fe, with an error probably <0.1×10-4. Although there is a small contribution to each of these figures from orbital paramagnetism and, at the higher temperature, from the dependence of spin-wave amplitudes on field, the major contribution is almost certainly from the exchange-enhanced Pauli paramagnetism of itinerant d-band electrons. For this contribution to be as large as is observed for Ni, it seems necessary that the commonly accepted band structure of Ni be replaced by one with holes of both spins in the d-like bands. © 1966 The American Institute of Physics.