We have used ferromagnetic resonance to measure the temperature dependence of the saturation magnetization in three glassy alloys: I: Fe29Ni49P14B6Si2(Metglas 2826B), II: (Fe0.4Ni0,6)75P16B6Al3, and III: (Fe0.5Ni0.5)75P16B6Al3. In I we find that, for 4 ?T?300 K, the magnetization follows the relaxation M(T) =M0(1–BT3/2−CT5/2) with B and C values fairly close to those obtained using Mo¨ssbauer and vibrating sample magnetometer techniques. For II and III it is necessary to include the effects of spin wave energy renormalization, with temperature, to account for the variation of M over a comparable temperature regime. That is, the parameter B obeys the relation: B(T) =B0[1/(1−&agr;T5/2)]3/2. In terms of the spin wave stiffness this implies D=D0[1−&bgr; (T/Tc)5/2] meV‐A˚2where, again, the parameter values are in the range found for similar systems by neutron scattering.