We have used ferromagnetic resonance to measure the spinwave dispersion coefficient D and the temperature dependence of magnetization M(T) in thin films of an electrodeposited amorphous Co‐P alloy of ∠25 at.% P. From spinwave dimensional resonance, D=138±5 mev Å2 at 4.2°K, which is in substantial agreement with that expected from the coefficient of T3/2 in the low temperature magnetization (T<TC/3). These results indicate that long wavelength spinwave excitations are responsible for 90±8% of the observed decrease of magnetization at these low temperatures and that apparent discrepancies between results from inelastic neutron scattering and from low temperature magnetization measurements for amorphous ferromagnetic alloys should be reexamined.