The observation of spin‐wave resonance in Permalloy samples of extremely low anisotropy has been extended to liquid nitrogen temperature. Measurements at both room and liquid nitrogen temperature have been carried out at 3000 and at 4000 Mc/sec. At room temperature the complete experimental resonance curve can be explained at both frequencies on the basis of the spin‐wave resonance theory of Ament and Rado by using an average exchange stiffness constant,A, of (3.3±0.5)×10−6erg/cm and agfactor of 2.06±0.01. The agreement between experiment and theory would be destroyed if a Landau‐Lifshitz or Bloch damping term were included. The theory of Ament and Rado predicts that as the temperature is lowered the exchange broadening of the resonance line increases and the resonance field decreases. Both effects have been observed qualitatively but neither is as large as would be expected from the theory. It has been found that at a given temperature the plot of the imaginaryversusreal part of the equivalent permeability at 3000 Mc/sec differs only by a scale factor from the corresponding plot at 4000 Mc/sec. At room temperature the above frequency increase causes a decrease in the permeabilities of 30% from the corresponding values at 3000 Mc/sec, as compared to a predicted 15% decrease. The discrepancy between theory and experiment at the low temperature is about the same at one frequency as at the other. Since the corresponding resonance fields differ by a factor of two, any effects due to incomplete saturation seem to be ruled out.