To investigate the role played by cytokines in the natural progression of ARDS. The aims of this investigation are to (1) define the origin of cytokines released, (2) define the effect of cytokines on the severity of ARDS, (3) define the pathophysiologic role of cytokines in injury and repair of the lung (4) determine the effect of systemically released cytokines on organ function, (5) determine the effect of infections on cytokine release, (6) determine the effect of corticosteroid therapy on cytokine release.