Purpose: To develop an instrument designed specifically to assess the ă experience of relatives of patients who die in the intensive care unit ă (ICU). ă Methods: The instrument was developed using a mixed methodology and ă validated in a prospective multicentre study. Relatives of patients who ă died in 41 ICUs completed the questionnaire by telephone 21 days after ă the death, then completed the Hospital Anxiety and Depression Scale, ă Impact of Event Scale-Revised and Inventory of Complicated Grief after ă 3, 6, and 12 months. ă Results: A total of 600 relatives were included, 475 in the main cohort ă and 125 in the reliability cohort. The 15-item questionnaire, named ă CAESAR, covered the patient's preferences and values, interactions ă with/around the patient and family satisfaction. We defined three groups ă based on CAESAR score tertiles: lowest (= 69, n = 121, 29.3 %). Factorial ă analysis showed a single dimension. Cronbach's alpha in the main and ă reliability cohorts was 0.88 (0.85-0.90) and 0.85 (0.79-0.89), ă respectively. Compared to a high CAESAR score, a low CAESAR score was ă associated with greater risks of anxiety and depression at 3 months ă [1.29 (1.13-1.46), p = 0.001], post-traumatic stress-related symptoms ă at 3 [1.34 (1.17-1.53), p