Mg sea surface temperature (SST) records from different planktonic foraminifera (G. sacculifer and G. ruber), size fractions, and core depths (1600 and 2600 m) suggest similar amplitudes of cyclic change over the last 425 kyr. However, there are significant differences in the detail recorded by different size fractions and between cores in close geographic proximity. These differences may be induced by dissolution, but artifacts resulting from divergent cleaning protocols and a dependency of the magnitude of these on preservation status cannot be ruled out. These and issues such as reproducibility require greater scrutiny for the true significance and credibility of down core Mg SST variability to be established.