THE Taylor and Wright Valleys, McMurdo Sound, Antarctica, contain a series of lakes of particular geochemical interest. Several of these, including Lakes Bonney, Joyce, Fryxell and Hoare in the Taylor Valley and Lake Vanda in the Wright Valley, are, although ice covered, not completely frozen. They are also saline and strongly density stratified, with the waters at the bottom of the lakes containing large amounts of dissolved solids1–7. A recent survey of the concentrations of a number of trace elements in the water of the above lakes has been undertaken with the intention of elucidating the origin of the salts present in them8. This has shown that it is possible that Lake Bonney has had a sea water origin and that Lake Fryxell may also have contained some sea water in the past, but that it is unlikely that the other lakes considered here were of marine origin.