We have remeasured the δ18O of O2 and δ15N of N2 in trapped gases in the GISP2 and Vostok ice cores, and recalculated variations with depth in the δ18O of paleoatmospheric O2. The new records have improved precision and resolution, allowing us to correlate the two ice cores using δ18O of O2 as a time-stratigraphic marker with about half the previous uncertainty in relative ages. We transfer the relative timescales from the gas records to the ice by correcting for differences in the age of the ice and the trapped gas. We then compare records of isotopic temperature vs. time for the GISP2 and Vostok cores. Our comparison confirms that all 6 long (> 2 kyr) interstadial events found in GISP2 between 35-75 ka also occur at Vostok, and strongly suggests that the 9 short GISP2 interstadials occurring within this time period have counterparts at Vostok as well. On average, long and short interstadial events at Vostok and GISP2 are in phase. Various uncertainties, however, allow for corresponding events to be out of phase by as much as 1.4 kyr on average. The near synchroneity in climate change between GISP and Vostok during interstadial events contrasts with the climate phasing during Termination 1, when long, slow warmings as well as millennial events were largely out of phase.