The alpha <----> gamma transformation was studied by thermomagnetic measurements in the two-phase (alpha and gamma) region of Fe-Ni alloys. The Fe96Ni4 and Fe90Ni10 samples were prepared by melt quenching and cold-rolling. A typical hysteresis phenomenon in the phase transformation was found in all alloys but the sample preparation had no influence on the character of thermomagnetic curves even if low temperature saturation magnetization data indicated a higher amount of retained gamma -phase in the melt-quenched alloys. The hysteresis depends on the Ni content and on the maximum of temperature reached during heating.