Objective: End-of-life decisions are based on objective and subjective criteria. Previous studies identified substantial subjective biases during end-of-life decisionmaking. We evaluated whether in-ICU patient's birthday influenced management decisions. Design: We used a case-control design in which patients spending their birthday in the ICU (cases) were matched to controls on center, gender, age, severity, type of admission, and length of ICU stay before birthday. Setting: 12 ICUs in French hospitals. Patients: The cases and controls were patients with ICU admissions[48 h over a 10-year period. Interventions: None. Measurements and main results: Compared with the 1,042 controls, the 223 cases were more often trauma patients and received a larger number and longer durations of life-sustaining interventions. This increased intensity of life support occurred after, but not before, the birthday. The cases had longer ICU stay lengths. ICU and hospital mortality were not different between the two groups. End-of-life decisions were made in 22% and 24% of cases and controls, respectively. However, these decisions were made later in the cases than in the controls (18 [5-33] versus 9 [3-19] days). Conclusions: Our finding that patients who spent their birthday in the ICU received a higher intensity of lifesustaining care and had longer ICU stays but did not have significantly different mortality rates compared with the controls suggests the use of nonbeneficial interventions. Staff members caring for patients whose birthdays fall during the ICU stay should be aware that this feature can bias end-of-life decisions, leading to an inappropriate level of care.