The straightforward core pathobiologic facts needed for the clinician's basic understanding of the clinical course and pathophysiology of progressive acute respiratory insufficiency (ARI) seen in surgical practice are summarized in the opening paragraphs. The remainder of the article provides the detailed evidence for elucidating the morphogenesis, i.e., the sequence of pathologic events, which determines the natural and the therapeutically altered clinicopathophysiologic courses of ARI. The attempt is to integrate observations concerning altered structure, cell biology, pathophysiology, physiologic function test data, bioengineering principles, clinical course, therapeutic management, and historical aspects of the disease process, into a detailed multidisciplinary but comprehensive explanation of this very complex, difficult disease process.