Ventral　striatum　(VS)　processes　rewarding　and　punishing　stimuli.　Women　and　men　vary　in　externalizing　and　internalizing　traits,　which　may　influence　neural　responses　to　reward　and　punishment.　To　investigate　sex　dif-ferences　in　how　individual　traits　influence　VS　responses　to　reward　and　punishment,　we　curated　the　data　of　the　Human　Connectome　Project　and　identified　981　(473　men)　subjects　evaluated　by　the　Achenbach　Adult　Self-Report　Syndrome　Scales.　We　processed　the　imaging　data　with　published　routines　and　extracted　VS　response　(beta)　to　win　and　to　loss　vs.　baseline　in　a　gambling　task　for　correlation　with　externalizing　and　internalizing　symptom　severity.　Men　vs.　women　showed　more　severe　externalizing　symptoms　and　higher　VS　response　to　monetary　losses　(VS-loss　beta)　but　not　to　wins.　Men　but　not　women　showed　a　significant,　positive　correlation　between　VS-loss　beta　and　externalizing　traits,　and　the　sex　difference　was　confirmed　by　a　slope　test.　The　correlations　of　VS-loss　vs.　exter-nalizing　and　of　VS-win　vs.　externalizing　and　those　of　VS-loss　vs.　externalizing　and　of　VS-loss　vs.　internalizing　traits　both　differed　significantly　in　slope,　confirming　its　specificity,　in　men.　Further,　the　sex-specific　relationship　between　VS-loss　beta　and　externalizing　trait　did　not　extend　to　activities　during　exposure　to　negative　emotion　in　the　face　matching　task.　To　conclude,　VS　responses　to　loss　but　not　to　win　and　their　correlation　with　externalizing　rather　than　internalizing　symptom　severity　showed　sex　differences　in　young　adults.　The　findings　highlight　the　relationship　of　externalizing　traits　and　VS　response　to　monetary　loss　and　may　have　implications　for　psychological　models　of　externalizing　behaviors　in　men.