A method for validating, on a worldwide scale, satellite measurements by comparison with ships of opportunity measurements has been derived. It has been applied to wind speed retrieved from the Geosat altimeter backscatter cross section for comparing the results obtained using either the smoothed Brown algorithm, the algorithms, the Chelton and Wentz algorithm, or the modified Chelton and Wentz algorithm. Among these three inversion Chelton and Wentz one best fits the ship reports at global scale, giving a bias less than 1 m s-1 in the whole wind speed range. In known windy regions, it retrieves wind speed values compatible with usually admitted values while the other algorithms give wind speeds lower by up to several m s-1. ¿American Geophysical Union 1992