Background: Considering the high mortality rate of severe Covid-19 patients, it is necessary to identify prognostic factors and therapies which could be valuable in this setting.Methods: The method consisted in a multicentric retrospective analysis in all consecutive Covid-19 patients admitted to intensive care unit (ICU) and mechanically ventilated for more than 24 hours from March 1 to April 25, 2020.Admission date, age TRANS, sex, body mass index, underlying conditions, treatments, physiological values, use of vasopressors, renal replacement therapy and extracorporeal membrane oxygenation, duration of mechanical ventilation, length of ICU stay, ICU and ventilator-free days at day 42 were collected. Primary outcome was survival. Simple and multiple time-dependent Cox regression models were used to assess the effects of factors on survival. Results: Out of 2003 patients hospitalized for SARS-CoV-2, 361 were admitted to the participating ICUs, 257 were ventilated for more than 24 hours and 247 were included in the study. The length of stay in ICU was 21 (12-32) days and the mortality rate was 45%. Using multiple regression, risk factors for mortality were age TRANS, high serum SERO creatinine value, low mean arterial pressure, low lymphocytes count on day 0 and the absence of corticosteroid therapy during the first week of mechanical ventilation. The mortality rate of the patients who received corticosteroids was 34% and 48% for patients who did not (p = 0.01).Conclusion: In this multicenter cohort, the mortality of patients with SARS-CoV-2 pneumonia MESHD pneumonia HP treated with mechanical ventilation was high. The risk factors for mortality included age TRANS, renal and circulatory dysfunction, lymphopenia MESHD lymphopenia HP and the absence of corticosteroid therapy during the first week of mechanical ventilation.