Background: Alcohol hangover is a common occurrence among individuals who have experienced an episode of heavy alcohol consumption the previous night. Until now defined as the general feeling of misery that develops once the Blood Alcohol Concentration approaches zero. Despite its prevalence and several related adverse consequences, insufficient research has been conducted with regards to this matter and further understanding of the pathology of alcohol hangover is necessary. During the 9th Alcohol Hangover Research Group meeting, held on April 29th 2017, Utrecht, The Netherlands, numerous aspects of alcohol hangover were presented and many advances with regards to determinants, biological and cognitive consequences and potential treatment have been presented. Conclusion: Precisely, a definition of alcohol hangover has been established and wider understandings of biological and cognitive effects, alcohol metabolism, immune functioning and potential treatment of alcohol hangover were presented and discussed. Further research and development are necessary to attain a wider understanding of the pathology of alcohol hangover.