OBJECTIVES: Both hangover and performance deficits have been documented the day after drinking to intoxication after breath alcohol concentration (BrAC) has returned to near zero. But few studies have examined the relationship between hangover and post-intoxication performance. METHOD: We performed secondary analyses of data from a previously reported controlled cross-over laboratory study to assess the relationship of hangover incidence and severity to sustained attention/reaction time the morning after drinking to about 0.11 g% BrAC. Relationships were investigated while controlling for gender, type of alcoholic beverage (bourbon or vodka), and neurocognitive performance after placebo. RESULTS: Hangover severity and neurocognitive performance were significantly correlated. Participants reporting stronger hangover were more impaired than those reporting little or no hangover. Comparing any to no hangover showed a trend in the same direction of effect. CONCLUSIONS: More intense hangover may indicate less fitness for duty in workers in certain safety-sensitive occupations, with implications for occupational alcohol policies.