Nineteen years of Advanced Very High Resolution Radiometer Multi-Channel Sea Surface Temperature (AVHRR MCSST) data were used to calculate monthly averages of sea surface temperatures (SSTs) for a large region of the Southern Ocean centred on Macquarie Island. Between October and February, the MCSST data were a reliable source of SSTs north of 60°S, but their quality (i.e. spatial and temporal density) was degraded severely at higher latitudes. Between April and August, the interpolated MCSST data were found to be unreliable in the study area, even at latitudes as low as 45°S. A specific problem has been identified to the west of Tasmania in the winter interpolated climatology which is likely an artefact of interpolation of sparse data. The poor coverage of valid MCSSTs during this time limits the data's application for many uses. Although the limitations of the MCSST data set are well recognised, the possibilities for ecological applications of these data remain largely unexplored and unquantified. The potential exists to maximize the information available from this and other similar data sets by determining the appropriate spatial and temporal scales at which they are best applied to biophysical models.