As a result, we propose to perform a one-year prospective audit of all ALI and ARDS patients managed in 40 ICUs from 17 Spanish provinces (15 provinces in the mainland and 2 provinces in the Canary Islands). We intend to collect data from all patients admitted with or developing ALI/ARDS with the aim to understand the epidemiology and natural history of acute lung injury. These provinces are scattered through the Spain and are representative of the demographic differences across the country.