This issue of Clinics in Chest Medicine focuses on Acute Respiratory Distress Syndrome and covers topics such as: Epidemiology and Definitions of ARDS and Early Acute Lung Injury, Environmental Risk Factors for ARDS, Clinical and Biological Heterogeneity in ARDS: Direct vs. Indirect Lung Injury,Obesity and Nutrition, Important Immunomodulators in ARDS?, Beyond SNPs-Genetics, Genomics and Other Omic Approaches to ARDS, Clinical Approach to the Patient with ARDS, The Immunocompromised Patient with ARDS: Role of Invasive Diagnostic Strategies, Clinical Trial Design in Prevention and Treatment of ARDS, Beyond Low Tidal Volume-Ventilating the Patient with ARDS, Prone Positioning in ARDS, and more!