We have imaged the magnetic domain structure of several heterogeneous CoxAg1−xalloys by using scanning electron microscopy with polarization analysis. These images show that extended domain structures exist in both the as‐deposited samples and in samples annealed at moderate temperatures. This suggests that a significant fraction of the cobalt in these materials does not contribute to the giant magnetoresistance. Only those samples annealed at 600 °C and containing less than 40% cobalt by volume show no domain structure. ©1995 American Institute of Physics.