Outcome in acute respiratory distress syndrome (ARDS) is influenced by a number of factors, including the nature of the precipitating condition and the extent to which multiorgan failure ensues. Most studies of potential therapeutic interventions have been unsuccessful due to the enrollment of limited numbers of patients with a wide variety of pathologies of varying severity. Moreover, the value of initiating single-agent interventions at varying time points in what is an evolving and complex inflammatory process must be questioned. Mortality may therefore represent an inappropriate end-point for clinical trials, which are increasingly focusing on ventilator-free days. Despite these uncertainties, survival appears to be improving, possibly due to the application of supportive techniques in a protocol-driven fashion to patients in whom the underlying condition has been rigorously treated.