Idiopathic bronchiolitis obliterans with organizing pneumonia (BOOP) is a clinicopathologic syndrome characterized by an indolent course and favorable prognosis. This report describes five patients with a fulminating and life-threatening variant of this syndrome. Four patients presented with respiratory failure requiring respiratory assistance and positive pressure ventilation. Early recognition of the entity and prompt initiation of corticosteroid therapy in three patients was instrumental in preventing mortality. Our findings suggest that idiopathic BOOP may be the underlying pathology in a number of patients presenting with ARDS. Since corticosteroid therapy may improve survival in these patients, clinicians should heighten their index of suspicion for this entity. Early histologic diagnosis and initiation of corticosteroid therapy should be considered in patients with unexplained ARDS.