The total power loss under alternating flux at power frequencies and zero applied stress conditions is an important criterion for the manufacturer and user of soft magnetic materials. The total power loss may be divided into three major types, namely the static hysteresis loss, classical eddy current loss and excess eddy current loss. It has been shown that the excess eddy current loss is responsible for approximately 90% and 50% of the total power loss of wide amorphous ribbon and grain-oriented silicon-iron respectively. Therefore it is possible to make comparisons of the causes and magnitude of the excess eddy current loss in these materials. The origin of the excess eddy current loss in grain-oriented 3% silicon-iron has been attributed to many causes. The feasibility of each of the suggestions as a possible cause of the excess eddy current loss of amorphous ribbon material is considered. It is concluded that the principal cause of the excess eddy current loss in amorphous ribbons is the non-sinusoidal non-uniform and non-repetitive domain wall motion which is the source of the observed non-sinusoidal and localised variations of the flux density.