Satellite ocean color data from the Sea-viewing Wide Field-of-view Sensor (Sea WiFS) were used to examine distributions of chlorophyll concentration within the Southern Ocean for the period October 1997 through September 1998. Over most of the Southern Ocean, mean chlorophyll concentrations remained quite low (30 ¿S) was estimated to be 14.2 Gt C yr-1, with most production (~80%) taking place at midlatitudes from 30¿ to 50 ¿S. Primary production at latitudes >50 ¿S was estimated to be 2.9 Gt C yr-1. This is considerably higher than previous estimates based on in situ data but less than some recent estimates based on CZCS data. Our estimated primary production is sufficient to account for the observed Southern Hemisphere seasonal cycle in atmospheric O2 concentrations. ¿ 2000 American Geophysical Union