The reflex effects produced by sensory receptors of the lungs have been reassessed. Increase in activity of pulmonary stretch receptors causes inhibition of inspiration and bronchodilation. The low-threshold pulmonary stretch receptors are responsible for Head's paradoxical reflex and the deflation reflex. The recent observations on the effects of left atrial injections of histamine show that histamine does not produce tachypnea through stimulation of irritant receptors. It is established that gradual stimulation of type J receptors (e.g., by histamine) produces tachypnea (in cats and rabbits), increase in functional residual capacity (rabbit), reflex bronchoconstriction (cat and rabbit), increase in laryngeal resistance (cat), and cough (man).