The prostaglandins are a group of pharmacologically potent lipid compounds whose role in pulmonary pathophysiology remains to be defined. There is not question that these compounds can induce constriction (PGF) or relaxation (PGE) of the smooth muscle in bronchi and pulmonary vessels. There is no question that the lungs are a major site of both the synthesis and degradation. These facts make speculation about the role of the prostaglandins in pulmonary disorders a tempting exercise. However, the current paucity of clinical data prevents any valid assessment of such speculation at this time and emphasizes the need for continued investigation of the role of prostaglandins in patients with lung disease.