Resonant magnetic field and linewidth of bulk nickel were determined between −160 °C and room temperature at the frequencies of 9.2, 19.7 and 26.2 Gc/s. At 19.7 and 26.2 Gc/s the resonance-field shift is found to be proportional to the anisotropy field. Below −90 °C the linewidth can be described by the independent-grain theory. For temperatures above −90 °C the validity of the dipole-narrowing model is discussed. At 9.2 Gc/s resonance field and linewidth are strongly influenced by additional absorption peaks caused by domain structure.