Marine isotope stages (MISs) 11 and 12 (~460--380 ka) contain what may be the most extreme climate conditions of the last 500,000 years and occurred at a time when Earth received a similar amount of solar insolation as the most recent glacial-interglacial cycle. Two high-deposition rate sediment cores, Ocean Drilling Program Sites 1059 (31.6¿N, 75.4¿W, 2985 m) and 1055 (32.6¿N, 76.2¿W, 1799 m) from the western North Atlantic were studied in order to examine the nature of millennial-scale variability in North Atlantic surface and thermohaline circulation during this time interval. Detailed records of δ18O and δ13C in the benthic foraminifera species Cibicidoides wuellerstorfi and the planktonic species Globigerinoides ruber (white) as well as detailed records of carbonate content were generated for both sites. These records suggest rapid variability in the strength of North Atlantic Deep Water production throughout MISs 11 and 12. Most of the observed changes in deep-water circulation appear to be associated with or coupled to changes in sea-surface hydrography. The duration of interglacial conditions during MIS 11 (20,000--30,000 years) is much longer than subsequent interglacial stages. Combined δ18O measurements and Mg/Ca based temperature estimates from G. ruber suggest sea-surface temperatures increased 2--3¿C across the MIS 12--MIS 11 transition.