A climatology of Antarctic sea ice extent based on 20 years of data (1973–1992) is presented, including measures of interannual variability and extrema. In the first half of the year the greatest variability is found in the Western Hemisphere, particularly in the Weddell and Ross Sea regions, while in the second semester the variability displays a considerable degree of zonal symmetry. We have used this dataset to explore the possible links between Antarctic sea ice extent and the Southern Oscillation Index (SOI). To do this we have calculated their correlation for all pairings of calendar months, as well as with the SOI taken from the year before and subsequent to that of the time of the sea ice data. Most of the correlations assume their largest magnitude when the SOI leads the anomalies in the sea ice, but these differ considerably between the three ocean basins. The extent of Indian Ocean sea ice in the months April through July is positively correlated with the SOI during most of the previous 12 months. The correlations over the Pacific are sizable only for spring sea ice correlated with the SOI in most of that same year. There appears to be no relation between previous SOI and Atlantic ice in any month. The evidence of sea ice conditions preceding SOI values is not as clearly marked but is present. Guided by the results and hypotheses of earlier authors, we examined the possibility of links between the SOI and sea ice in four key sectors around the Antarctic coast, namely, the southwest Indian Ocean, the southwest and southeast Pacific Ocean, and a sector to the west of the Ross Sea. In general, the correlations for these domains are stronger that those found over the entire ocean basins, supporting suggestions that there are important key regions over which the Antarctic sea ice influences, and is influenced by, the Southern Oscillation. One of the strongest relationships is between ice extent in the southeast Indian Ocean in the months April through October and the SOI in the previous 12 months.