ABSTRACTA case is made for the stability of the East Antarctic Ice Sheet during Pliocene time from landscape development and surficial sediments in the Dry Valleys sector of the Transantarctic Mountains. The alternate hypothesis of Pliocene meltdown requires atmospheric temperatures 20°C above present values, late Pliocene ice-sheet overriding of the Transantarctic Mountains, and possible rapid late Pliocene mountain uplift of 1000–3000 m. The geomorphological results suggest that these conditions were not met in the Dry Valleys region. Rather, Pliocene mean annual atmospheric temperatures were at most only 3°to 8°C above present values; ice-sheet overriding occurred in Miocene time (>13.6 Ma); Pliocene glacier expansion was limited; and Pliocene surface uplift was only about 250 to 300 m. These conclusions are based on field studies in Taylor and Wright Valleys, in the western Asgard Range, and in the Quartermain Mountains. The chronology comes from numerous40Ar/39Ar dates onin-situvolcanic ashes that occur in stratigraphic association with unconsolidated diamictons in the western Dry Valleys, basaltic lava flows interbedded with widespread tills in Taylor Valley, and reworked basaltic clasts in alpine moraines in east-central Wright Valley. The combined evidence from the Dry Valleys region indicates that slope evolution was severely restricted throughout Pliocene time, and has been so since at least the middle Miocene. The implication is that most of the Dry Valleys landscape is relict and that it reflects ancient erosion, possibly under semi-arid climate conditions, prior to middle-Miocene time.