This aim of this study was to assess the clinical utility of quantitative ST-segment depression (STD) for refining the risk stratification of non-ST elevation acute coronary syndromes in the prospective, multinational Global Registry of Acute Coronary Events (GRACE). Quantitative measurements of STD on admission electrocardiograms were evaluated independently by a core laboratory, and their predictive value for in-hospital and cumulative 6-month mortality was examined. Although more severe STD is a marker of increased short- and long-term mortality, it is also associated with higher risk clinical features and biomarkers. Thus, after adjustment for these clinically important predictors, quantitative STD does not provide incremental prognostic value beyond simple dichotomous evaluation for the presence of STD. Furthermore, adopting quantitative instead of the prognostically proven qualitative evaluation of STD does not improve risk discrimination afforded by the validated GRACE risk models. In conclusion, the findings do not support the quantification of STD in routine clinical practice beyond simple evaluation for the presence of STD as an integral part of comprehensive risk stratification using the GRACE risk score.