 This study will allow entry of patients who have fulfilled criteria for ALIARDS for up to 7 days. Treatment will be initiated after patients have met criteria for at least 3 days. Treatment with GM-CSF may prove both safe and effective within the first 1-2 days of lung injury. However, the present study will not address that question. It is unlikely that the opportunity for improved outcome will be lost by delaying therapy for up to 3 days based on the proposed mechanisms by which GM-CSF might benefit this patient population. Similarly, the decision to treat for 14 days will allow for improved outcome in patients with non-resolving ARDS by reducing the incidence of ventilator-associated pneumonia and by decreasing pathologic fibroproliferation. 