AbstractBACKGROUND\nPATIENTS AND METHODS\nRESULTS\nCONCLUSIONS\nWomen with atrial fibrillation (AF) may be treated less actively with oral anticoagulation (OAC) than men.\nWe assessed sex differences in the implementation of stroke risk stratification with CHADS₂ and CHA₂DS₂-VASc scores and reasons not to use OAC in 1747 AF patients suffering their first cerebrovascular event after the AF diagnosis.\nWomen were older and had more often a high stroke risk (CHADS₂/CHA₂DS₂-VASc ≥2) than men (p < .001). On admission, 46.4% of women and 48.2% of men were on OAC with no sex difference (p = .437). However, of patients without OAC, 74.4% of women and 49.5% of men should have been on OAC based on CHADS₂/CHA₂DS₂-VASc ≥2 (p < .001). Conversely, 34.8% of men and 17.5% of women on OAC had a low or moderate risk (CHADS₂/CHA₂DS₂-VASc 0-1, p < .001). A valid reason to omit OAC was reported in 38.6% of patients and less often in women (p < .001).\nOAC was underused in high-risk AF patients, particularly women, but prescribed often in men with low or moderate stroke risk. Reasons for omitting OAC treatment were poorly reported, particularly for women. KEY MESSAGE Women were at higher stroke risk, but were less often treated with oral anticoagulation (OAC). Men were more often on OAC at low or moderate stroke risk. Reasons for omitting guideline based OAC were poorly reported, particularly for women.