We attempt to quantify the Antarctica annual mass balance by estimating the seasonal water mass exchange among the main surface reservoirs (oceans, atmosphere, continents and ice sheets) using various data sources. These data include Topex-Poseidon altimetry and in situ ocean temperature data, soil moisture and snow depth data, and atmospheric surface pressure data. We calculate the seasonal (annual) variations of ocean water mass, continental waters and atmospheric water vapor contributions respectively. We find that the observed ~9 mm annual mean sea level variation caused by water mass exchange with the other reservoirs cannot be totally explained by the combined contributions of snow, soil moisture and atmospheric water vapor. A residual signal, of 3 mm amplitude, maximum at the end of December, is observed that we attribute to the Antarctica annual mass balance. This residue is consistent with existing understanding of Antarctica precipitation. ¿ 2000 American Geophysical Union