To assess the incidence of hangover we: (1) reviewed the experimental and survey literature; (2) performed secondary analyses on two large population surveys; and (3) calculated the incidence of hangover among young adults participating in several randomized trials we conducted on the aftereffects of heavy drinking. Survey data included adults admitted for alcohol detoxification, community adults who ever got "tipsy" or "high", adolescents in high school who ever drank heavily, adults who drank heavily in the past 12 months, and university students. Most of the experimental trials brought participants to intoxication. The consistency of findings across study designs, populations, and referenced time period suggests that around 23% of the population may be resistant to hangover. Since propensity for hangover may affect drinking patterns, further research on the consequences and predictors of hangover insensitivity is warranted.