2010, Article / Letter to editor (Critical Care, vol. 13, iss. 6, (2010), pp. 341)Predictive models, such as acute physiology and chronic health evaluation II (APACHE-II), are widely used in intensive care units (ICUs) to estimate mortality. Although the presence of delirium is associated with a higher mortality in ICU patients, delirium is not part of the APACHE-II model. The aim of the current study was to evaluate whether delirium, present within 24 hours after ICU admission, improves the predictive value of the APACHE-II score. Delirium in ICU patients present within 24 hours after ICU admission, is associated with increased in-hospital mortality. Adding delirium to the APACHE-II score does not improve its accuracy in predicting in-hospital mortality.