The in‐plane magnetic saturation field and the intensity of small‐angle x‐ray scattering were observed for some amorphous, ferromagnetic Co‐P alloy films (22.5 at. % P), 3l μm thick, produced by electrodeposition. Annealing the amorphous films redcues both the intensity of small‐angle x‐ray scattering adn the in‐plane magnetic saturation field. The x‐ray scattering observations have been interpreted in terms of oriented, ellipsoidal scattering regions of high (or low) cobalt concentration, and therefore of high (or low) magnetization. Anisotropy energies calculated with a magnetostatic model, using observed x‐ray scattering data, are consistent with measured in‐plane saturation fields, both for as‐deposited and for annealed films. The time‐temperature dependences observed in annealing experiments suggest that the annealing effects are associated with reductions of composition inhomogeneities by atomic scale diffusion. Our results indicate that internal demagnetizing effects associated with anisotropic microsstructure contribute to perpendicular easy‐axis magnetic anisotropy in these amorphous ferromagnetic films.