We have obtained the magnetospheric electric potential distribution along the path of Polar using ion data from Hydra and magnetic field data from MFE. We used the technique described by Whipple et al. [1998> to identify ion drift paths that intersected the spacecraft path at two different locations and times. The difference in energy of the ions at the two times, under certain restrictive assumptions, indicates the potential difference between the two locations. We did this for five minute intervals over 1.5 hours and summed these differences to obtain the potential variation along the spacecraft path. The results agree well with that obtained by the Polar Electric Field Instrument, and are consistent with a co-rotation potential plus a small tailward field of magnitude 0.10 mV/m. This technique can complement and aid in the interpretation of other electric field data, or provide electric field data where such instruments are not available. ¿ 1999 American Geophysical Union