In this paper we report the results of two and a half years of measurements of the ground electric field at the Pacific coast of Mexico. The analysis of the voltage itself does not show any distinguishable feature that could be correlated to earthquakes. Fourier analysis, however gives clear patterns of the electric field prior to the four MS,W>6 earthquakes that occurred in the zone during the time interval considered. ¿ American Geophysical Union 1995