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Variability of Total Electron Content (TEC) in the equatorial anomaly region of the ionosphere can be studied extensively using the results of measurements taken by the NASNCNES satellite. TOPEXFoseidon. which provides global ocean coverage (0 to 360 degrees longitude. -66 to 66 degrees latitude). The NASA radar altimeter (NRA) is the first space-borne dual-frequency altimeter capable of accurately measuring vertical ionospheric TEC below 1340 km.. TOPEX TEC observations have already been used to support results from an ionospheric measurement campaign that was conducted in equatorial anomaly regions of South America by Phdlips Laboratory in Spring. 1994. The best agreement in TEC values is seen during intervals of longitudinal proximity of the satellites' paths.Vertical measurements from TOPEX are obtained at a rate of one per second at 5.3 and 13.6 GHz. along the same surface tracks every 10 days during which global ocean coverage is accomplished. TOPEX data records from 9/92 to 9/95 have been processed and reduced to one CDROM disc using one degree averaging over 110 !un. along track for evaluation of TEC measurements. Various plotting programs have been developed to represent the data for observation of TEC value,s and the occurrence of the equatorial anomaly. To facilitate f u v ther TEC studies, interface software has been prepared to provide easy access to specific dates. local times and longitudes with identification of anomaly formation and structure. The TOPEX over-ocean data can be used as a supplement to land based measurements in applications to ionospheric research at low and middle 1atitudes.This study focuses on comparisons between TOPEX vertical TEC data and GPS equivalent vertical TEC measurements taken near the East and West coastal regions of South America. Also the Phillips Laboratory Global Parameterized Ionospheric Model (PIM) is utilized in an effort to estimate slant to vertical conversion errors. Previous ionospheric observations have measured Total Electron Content (TEC) values at fixed land based locations. These observations suggest the existance of longitudinal variations in TEC values. Complementing ground data, the current NASA TOPEX mission is providing TEC data collected over oceans as a function of latitude, longitude and time starting from September 1992. With this broad data base, we show a more complete picture of the longitudinal dependance between the Atlantic and Pacific ocean regions and relate this dependance to plasma drifts. Periods during June and December solstice, and March and September equinox in the years 1992. through 1995. are picked to study the low-latitude regions spanning the Atlantic and Pacific oceans. TEC isodensity contours are presented by latitude versus longitude at common local time. We corrolate these contours with results from the Phillips Laboratory ionospheric model.