The objective of this study was to determine the validity of French and English versions of the Older American Resources and Services (OARS) activities of daily living (ADL) questionnaire using a premorbid reference period among older emergency department (ED) patients. A sample of 404 ED patients aged 65 and over participating in a study of functional decline was invited to participate in a clinical assessment shortly after their ED visit. The OARS ADL questionnaire was administered either to the patient or a proxy informant at the ED visit. The clinical assessment was conducted by a nurse, blind to the OARS score, using the Functional Autonomy Measurement System (SMAF). Disability scores for the OARS and SMAF were computed, based on the patient's premorbid status. Assessments were conducted in 213 patients (52.7%). The OARS summary scores, a total and an ordinal score, were highly correlated with the SMAF total disability score (Spearman's r of 0.80 and 0.79, respectively). Similar correlations were found for French and English versions. The OARS ADL questionnaire with a premorbid reference period appears to be valid when administered in the ED, both in French and English.