Efficient techniques for mapping the marine gravity field with Geosat Exact Repeat Mission (ERM) data are demonstrated. Geosat has completed more than fifty-two 17-day, global ERM repeat cycles and has collected roughly 50 million observations of geoid undulations or, more precisely, sea surface topography. Because the global ground track repeats every 17 days, the ERM observations are highly redundant. By averaging the repeat cycles, very precise profiles of alongtrack geoid undulations are obtained for a region of the southeast central Pacific. Without any crossing-arc, orbit adjustments, these profiles are shown to be repeatable to within 10 cm over their entire 3000 km length (i.e., to three parts in 108). This southeast central Pacific region contains a portion of the East Pacific Rise as well as some cross-grain gravity field lineations and is therefore of considerable geophysical interest. In addition to profiles of alongtrack deflections of the vertical, regularly gridded gravity anomalies are derived for this region and portrayed in color. The procedure used for recovering gravity has two stages: in stage 1, alongtrack deflections of vertical are derived by fitting cubic splines to alongtrack heights, computing alongtrack slopes at standardized latitudes, and then averaging slopes for coincident passes; in stage 2, gridded, band-limited gravity anomalies are recovered from deflections by using fast Fourier transform techniques to accomplish the necessary inverse Vening Meinesz transformation. High-precision GEM-T1 orbits are used and crossover adjustments are not performed. The operational Navy Astronautics Group orbits are shown to have systematic errors which may be as large as 10 m.