Geosat altimeter data taken during a 1-year period over the oceans around South Africa have been processed. This area is well known for its many interesting current systems and bathymetric features. The investigation has focused on the elimination of the radial orbit errors by means of the crossover minimization technique and on the computation of mean sea surfaces and the determination of mesoscale sea surface variability. For three tracks over this area the collinear tracks analysis technique has been applied to investigate in detail both the mesoscale ocean surface variability and the horizontal component of the gravity disturbance vector. Various interesting geophysical and oceanographic features are discussed. In addition, the recovered Geosat radial orbit error over this area is analyzed, and the global distribution of the radial orbit errors is estimated.