A large fraction of the available electric field data from the plasma wave instrument (PWI) on the Dynamics Explorer (DE) 1 satellite has recently been searched for events with large-amplitude (over 100 mV m-1) electric fields. The magnitude and distribution of these peak events as functions of altitude have been determined. The largest amplitudes were found between 1.4 and 2.5 RE and the probability of finding large electric fields was greatest in the range of 1.5 to 1.7 RE. However, when the measured electric field values are ''mapped'' to the Earth's surface in order to account for the geometry of the geomagnetic field lines, then the mapped values always increase with increasing altitude. This radial dependence is considered to be evidence for magnetic field-aligned electric fields. The largest electric field that was detected with the DE 1 instrument had a magnitude exceeding 840 mV m-1 and was found at 1.45 RE. This field appears to be associated with a low-frequency wave, whereas the more commonly observed large-amplitude events have longer durations, are generally found at higher altitudes, and appear to be due to static electric fields. It appears that two types of phenomena are being observed. A study of all electric field measurements, rather than just those with large amplitudes, was also conducted. It was found that at subauroral latitudes the average mapped electric field is nearly constant with altitude, as it should be where there are no magnetic field-aligned potential drops. Small variations can be accounted for by long-term changes in geomagnetic activity. However, within auroral latitudes the average value of the mapped electric field increases as altitude increases. The largest gradients are found between 1.3 and 2 RE. There is evidence for a ''split'' potential distribution, with an additional potential drop located above 2.7 RE. ¿ American Geophysical Union 1993