Abstract Introduction: Racial differences exist in sleep duration and circadian timing, however it is unknown whether these differences extend to cognitive performance. The current study investigated the role of ancestry on sleep and performance before and after a 9h advance of the sleep/wake episode. Methods: Twenty African-Americans (9F; 32.1 ± 7.5yr) and 17 European-Americans (8F; 29.7 ± 5.7yr) completed the study. Participants were scheduled to four baseline days each with 8h time in bed based on their habitual sleep schedule such that sleep and circadian rhythms were aligned. The sleep-wake schedule was then advanced 9h earlier (misaligned) for three days. Total sleep time (TST) was assessed with actigraphy. The Automated Neuropsychological Assessment Metrics (ANAM) test battery was administered every 3h each day starting 2h after waking. Tests included a simple reaction time task (SRT) and Stanford sleepiness scale (SSS). Mixed model ANOVAs assessed the effects of ancestry (African-American or European-American) and condition (aligned or misaligned) on sleep and performance. Results: TST was reduced on misaligned days compared to baseline (F=18.67, p<0.001) and African-Americans slept less compared to European-Americans (F=8.58, p<0.01), especially on the first two misaligned days when the difference was 47 and 59 minutes respectively (F=6.67, p<0.01). Compared to baseline, misalignment increased SSS ratings (F=72.69, p<0.001), but did not affect the number of lapses (F=0.02, p=0.90) or median reaction time (RT)(F=0.02, p=0.88) on the SRT. While there was no effect of ancestry on SSS (F=0.22, p=0.64), there was a trend for lapses (F=3.55, p=0.07) and median RT (F=2.80, p=0.10) to be higher for African-Americans. On misaligned days, African-Americans performed worse than European-Americans at times corresponding to the end of baseline sleep (lapses, F=7.16, p<0.05; median RT, F=5.16, p<0.05). Conclusion: Racial disparities in sleep may be more prominent when the sleep episode is shifted, and there may be racial differences in the circadian regulation of performance. Results have implications for the sleep and performance of individuals undertaking shiftwork or transmeridan travel. Support (If Any): R01NR007677(CIE).