Background: Delirium is frequently encountered in hospital settings especially in the Intensive Care Unit (ICU), with an incidence of 42% to 87%. The aetiology of delirium is still unknown but research has shown that prevention and treatment is possible. Early detection is a necessary first step for successful treatment and prevention in the ICU. The Confusion Assessment Method for the ICU (CAM-ICU) is a rapid and easily administered screening instrument to detect delirium in the ICU setting and is based on the Diagnostic and Statistic Manual of Mental Disorders IV criteria (DSM-IV) The aim of this study was to validate the Dutch version of the CAM-ICU. Methods: The CAM-ICU was translated in accordance with standard translation guidelines. The validation study of the Dutch CAM-ICU version was performed in a large Dutch community hospital with a mixed ICU. The patients were tested by a geriatrician or a psychiatrist for clinical symptoms of delirium according to the DSM IV criteria (= reference standard), and the results were compared with independently scored CAM-ICU outcomes. Results: Thirty consecutive adult patients with Richmond Agitation and Sedation Scale (RASS) ≥-3 were assessed for delirium using the CAM-ICU and the DSM-IV criteria, resulting in 60 paired tests. Twenty-nine patients were included in the analysis. Based on the DSM-IV criteria 11 of 29 patients had delirium and 9 of 29 scored positive on the CAM-ICU. Only three patients were diagnosed differently by the geriatrician or psychiatrist and the CAM-ICU, two had a psychiatric disorder and one had been sedated and was therefore excluded. Agreement was calculated using crosstabs analysis, overall agreement was 93.1%. In our validation cohort the incidence of delirium was 37.9%. Conclusion: The translation of the Dutch CAM-ICU showed good correlation with the original English version and can therefore be used in a Dutch ICU. The results of the validation study showed very good agreement between the clinical diagnoses made by the experts and the detection of delirium using the Dutch CAM-ICU. The Dutch CAM-ICU reliably detects ICU delirium. It therefore provides the means for early detection, treatment and secondary prevention of ICU delirium. Copyright © 2009, Nederlandse Vereniging voor Intensive Care. All Rights Reserved.