Early diagnosis is mandatory in the adult respiratory distress syndromes, particularly in sepsis, and therapy should begin as soon as there is a reasonable suspicion that this problem is developing. Blood-gas changes cannot usually be appreciated clinically until the respiratory problem is quite severe. Accordingly, serial blood-gas analyses should be performed in any septic patient who has an increased chance of developing ARDS. Any deterioration in the patient's condition, blood gases, or ventilatory effort should be considered as an indication for early ventilatory assistance. Control of the primary process, high tidal volumes, PEEP, and careful dehydration are the mainstays of therapy. Serial blood gases and careful observation of the patient's effective compliance are essential to determine the optimal ventilator settings and the optimal PEEP. Early administration of massive steroids should be considered if the patient fails to respond to correction of the underlying etiologic problem (particularly sepsis), careful progressive dehydration, and optimal expansion of the alveoli (using high tidal volumes and/or PEEP).