A wet tropospheric correction for the Geosat altimeter data is derived from the special sensor microwave imager (SSM/I) water vapor products by subobjective mapping. The correction presents wavenumber spectral characteristics close to those of the original SSM/I data in the 200- to 2000-km wave band, and is filtered in the short wavelength domain. In both respects, it behaves significantly better than corrections derived from 4-day averages of the SSM/I data interpolated quadratically under the Geosat track. As an example, the along-track rms mesoscale variability is lowered by 3 cm for some tracks in the northeast Atlantic Ocean when this correction is applied rather than the correction of Wentz <1990>. This suggests that it inneed improves the altimeter data. ¿ American Geophysical Union 1992