Sea level variability, related to the eddy field activity, can be calculated from repeating tracks of altimetric data, such as the SEASAT 3-day repeat data (September 13 to October 10, 1978). If we consider the eddy field in geostrophic balance, the geostrophic relation gives the surface eddy velocities. Also, an estimation of the eddy kinetic energy can be deduced under the assumption of quasi-isotropy of the velocity variability. This approach is used in the northwest Atlantic and northwest Pacific through the processing of SEASAT data. High variability of sea surface topography (up to 20 cm) and high eddy kinetic energy (800--1600 cm2/s2) are detected in the vicinity of the Gulf Stream and the Kuroshio. Power spectra of the observed sea level fluctuations give wavelengths ranging from 100 to 900 km for time scales between 3 and 25 days. Maps of sea surface topography variability and eddy kinetic energy are presented and discussed.