Ammonia is an important chemical in industry. Accidental inhalation of ammonia has resulted in upper airway and bronchoalveolar injury, and even fatal inhalation of anhydrous ammonia has occurred. We present herein a 5-year follow-up on a patient who had no prior history of smoking or pulmonary symptoms and had overwhelming exposure to ammonia which resulted in acute respiratory failure with diffuse lung parenchymal and airway involvement. The extreme inflammation and desquamation of the mucosa of the central bronchial tree, as observed bronchoscopically, have apparently resulted in a hyperreactive bronchoconstrictive component. Because our patient had never smoked and had no history of pulmonary symptoms or wheezing, we speculate that both the central and the peripheral residual airway obstructions were a result of his inhalation injury. In addition, peripheral airway disease, suggested by the postbronchodilator flow-volume curves present during the first year of follow-up, has gradually cleared even though there is evidence of parenchymal scarring.