Background:　Alcohol　misuse　is　associated　with　externalizing　behaviors,　including　rule　breaking.　Studies　have　implicated　altered　reward　processing　in　externalizing　behaviors　and　alcohol　misuse.　Here,　we　investigated　whether　reward　or　punishment　reactivity　more　significantly　influenced　alcohol　use　severity　and　rule-breaking　behavior　in　young　adult　drinkers.　Methods:　We　curated　data　from　the　Human　Connectome　Project　and　identified　181　binge　(132　men)　and　288　nonbinge　(97　men)　drinkers　performing　a　gambling　task　during　brain　imaging.　Alcohol　use　severity　was　quantified　by　the　first　principal　component　of　principal-component　analysis　of　all　drinking　measures.　We　analyzed　the　imaging　data　using　published　routines　and　evaluated　the　results　at　a　corrected　threshold.　We　examined　the　interrelationship　between　imaging　and　clinical　metrics　with　mediation　and　path　analyses.　Results:　Compared　with　nonbingers,　bingers　showed　more　severe　rule-breaking　behavior　and　responded　significantly　faster　during　post-loss　than　during　post-win　trials.　Compared　with　nonbingers,　bingers　demonstrated　greater　inferior/middle　frontal　gyrus　and　cerebellum　activations　in　loss-predominating　blocks　but　no　differences　in　regional　responses　to　win-predominating　blocks,　relative　to　an　interblock　baseline.　The　right　caudate　body　showed　loss　reactivity　that　was　positively　correlated　with　the　rule-breaking　score.　No　regional　responses　to　wins　were　significantly　correlated　with　the　rule-breaking　score.　Mediation　and　path　analyses　demonstrated　significant　models　with　inferior/middle　frontal　gyrus　and　caudate　reactivity　to　loss　interrelating　rule　breaking　and　alcohol　use　severity.　Conclusions:　Punishment　rather　than　reward　reactivity　was　associated　with　alcohol　use　severity　and　rule　breaking　in　young　adults.　The　findings　highlight　the　roles　of　negative　emotions　in　psychological　models　of　externalizing　behaviors　and　alcohol　misuse.　©　2022　Society　of　Biological　Psychiatry