BACKGROUND: Patients aged over 90 are being admitted to intensive care units (ICUs) with increasing frequency. The appropriateness of such decisions still remains controversial due to questionable outcome, limited resources and costs. Our objective was to determine the clinical characteristics and outcome in elderly patients (≥ 90 years) admitted in a medical ICU, with an additional focus on medico-economic implications. METHODS: We reviewed the charts of all patients (≥ 90 years) admitted to our ICU. We compared them with all other ICU patients (< 90 years), sought to identify ICU mortality predictors and also performed a long-term survival follow-up. RESULTS: In the study group of 317 stays: median age was 92 years (IQR: 91-94 years); most patients were female (71.3%.). Acute respiratory failure (52.4%) was the main admission diagnosis; mean SAPS II was 55.6±21.3; half the stays (49.2%) required mechanical ventilation (duration: 7.2±8.8 days); withholding and withdrawing decisions were made for 33.4% of all stays. ICU and hospital mortality rates were 35.7% and 42.6% respectively. Mechanical ventilation (OR = 4.83, CI95%: 1.59-15.82) was an independent predictor of ICU mortality whereas age was not (OR = 0.88, CI95%: 0.72-1.08). Social security reimbursement was significantly lower in the study group compared with all other ICU stays, both per stay (13,160 vs 22,092 Euros, p< 0.01) and per day of stay (p = 0.03). CONCLUSION: Among critically ill elderly patients (≥ 90 years), chronological age was not an independent factor of ICU mortality. ICU care-related costs in this population should not be considered as a limiting factor for ICU admission.