We investigate ATSR's skin SST precision by comparing all the available high resolution (1 km) ATSR data coincident with global drifting buoy records for the months of February and March 1992. Comparisons are made at two spatial levels: using spatially averaged ATSR data, and at the full (1 km) resolution. SSTs in each case are derived using both the standard algorithm and one using the 3.7 &mgr;m and 11 &mgr;m nadir channels. The mean bulk-skin temperature bias is 0.45K (night) and 0.13K (day). The precision is greater: (i) at night than during the day, (ii) when 12 &mgr;m noise contamination in the standard SST product is removed, (iii) when using a 1/2¿ subset for which a corresponding 1 km match-up exists. Our highest precision subset has an r.m.s. scatter of just 0.25K and must approach the geophysical limit set by the inherent variability of the skin effect. ¿ American Geophysical Union 1995