Breathlessness is a common symptom in patients with respiratory disorders and contributes significantly to functional disability. Recent studies of the psychophysics of respiratory sensation suggest that dyspnea is a function of the forces generated by the respiratory muscles during the act of breathing and may simply represent the intensity of the sense of effort arising from central respiratory motor command signals. It is important to recognize the multidimensional nature of respiratory sensations that include not only sensory aspects but also affective and cognitive components. At present there are no established satisfactory means of treating dyspnea. Efforts to minimize abnormalities in ventilatory system impedance are limited by the largely irreversible nature of most chronic lung diseases. Sedatives and narcotic agents have not proved to be effective in altering perceptual responses and may have an adverse effect, worsening respiratory failure. Physical measures to improve overall conditioning and respiratory muscle performance may be most effective in relieving breathlessness and improving exercise capacity in patients with chronic lung disease.