Objective: To evaluate the incidence of major adverse cardiac events (MACE) at 1 year in emergency department (ED) patients with possible acute coronary syndromes, stratified by high sensitivity troponin (hs-cTnI) concentrations using sex-specific cut points compared with overall cut points. Methods: In a multicentre observational study of 2841 patients, presentation hs-cTnI concentrations were categorised using sex-specific (women 16 ng/L; men 34 ng/L) and overall (26 ng/L) cut points. The primary outcome was MACE occurring within 1 year of presentation. Patients with hs-cTnI values concentrations within these categories were reported by sex and 1-year MACE. Net reclassification improvement (NRI) was computed to measure the change in prediction after altering the hs-cTnI cut points, and was calculated separately for events and non-events. Results: Application of sex-specific 99th percentile cut points rather than the overall cut point of 26 ng/L, reclassified 25 females from having a non-elevated troponin to having an elevated troponin, and 29 males from having an elevated troponin value to having a non-elevated troponin value on presentation. Of these, 7 (28.0%) females and 12 (41.4%) males had a 1-year MACE. There was no reclassification improvement for those with or without 1-year MACE (NRIevents=-1.5%, 95% CI -4.0% to 1.1%; NRInon-events-0.04%, 95% CI -0.5% to 0.4%). Conclusions: Sex-specific cut points improve the identification of women but not men at risk for 1-year MACE. The net-effect across the whole ED population with possible cardiac chest pain is minimal. Lowering the clinical cut point for both sexes may be appropriate for prognostic purposes. Trial registration number ISRCTN No. 21109279, ACTRN12609000283279.