Multidimensional instruments for determining the severity and prognosis of chronic obstructive pulmonary disease (COPD) must be used in daily clinical practice.To develop and validate a new COPD severity score using variables readily obtained in clinical practice and to compare its predictive capacity with that of other multidimensional indexes. Data collected from a prospective cohort of 611 stable COPD patients were used to derive a clinical prediction rule that was later validated in a separate prospective cohort of 348 patients. In the multivariate analyses, six independent predictive factors were correlated with overall and respiratory mortality: health status, physical activity, dyspnea, airway obstruction (FEV(1)), age, and hospitalizations for COPD exacerbations in the previous two years. These create the HADO-AH score. Based on the β parameter obtained in the multivariate model, a score was assigned to each predictive variable. The area under the curve for 5-year mortality was 0.79 (95% CI, 0.74-0.83) in the derivation cohort and 0.76 (95% CI, 0.71-0.81) in the validation cohort. The HADO-AH score was a significantly better predictor of mortality than the HADO-score and the Body-mass index, Obstruction, Dyspnea, Exercise-index were statistically significant (p < 0.0004 and p = 0.021, respectively), but was similar to the Age, Dyspnea, and Obstruction-index (p = 0.345). The HADO-AH score provides estimates of all-cause and respiratory mortality that are equal to, or better than, those of other multidimensional instruments. Because it uses only easily accessible measures, it could be useful at all levels of care.