DATA COLLECTION: Data collection will web based, permitting conditional Data Collection screens, i.e. data collectors will be automatically guided as to which sections to complete based on data entered indicating whether Inclusion Criteria are met. Data collection will be done at 10am each morning. Our aim is to obtain a sample of at least 1000 ARDS patients within the cohort of patients receiving assisted ventilation. The reported incidence of ARDS in ICU patients varies, from 2.2% of ICU admissions develop ARDS in ALIEN, 7.1% in ALIVE Study, to 17.5% of Ventilated patients in KCLIP . A reasonable projection of the incidence of ARDS among patients admitted in ICUs can be estimated to approximate 5% of ICU admission. As a conservative estimate, if a medium-sized ICU admits 50 patients/month and collects data for four, 500 ICUs will be necessary to achieve this number.