Two hundred ninety-eight consecutive out-of-hospital cardiac arrest patients (70.3% male; median age, 60.2 yr [49.9-71.4]) were admitted in a tertiary cardiac arrest center in Paris (France). After multivariate analysis, higher admission copeptin was associated with 1-year mortality with a threshold effect (hazard ratio(5th vs 1st quintile) = 1.64; 95% CI, 1.05-2.58; p = 0.03). Day 3 copeptin was associated with 1-year mortality in a dose-dependent manner (hazard ratio(2nd vs 1st quintile) = 1.87; 95% CI, 1