One characteristic of patients with asthma is that their airways are exquisitely sensitive to a variety of inhaled stimulants. For example, their airways regularly become obstructed after inhalation of bronchoconstrictor substances at 1/100 to 1/300 of the concentration required to produce a similar response in normal persons.^{1 2 3 4} This airway hyperresponsiveness is nonspecific: patients react to low concentrations of agents of different chemical classes as well as to substances that are not smooth-muscle constrictors.⁵ The recent identification of a new family of bronchoconstrictors, the sulfidopeptide leukotrienes C, D, and E (previously termed slow-reacting substance of anaphylaxis, or SRS-A),^{6 7 8} allows further study . . .