The planar Hall effect in ferromagnetic Ni-Fe alloys (Ni content at 100%, 80% and 50%) is observed. At room temperature it is found that in addition to the quadratic dependence on magnetization there also exists a parabolic dependence on the applied field for a field above the magnetic saturation. This is explained by assuming the existence of an effective internal field. It was also found that the planar Hall constants show marked variation with composition.