It is conceivable that the subjects who have phonatory disorders, in comparison with normal individuals, exert a greater expiratory effort when phonating loudly. Furthermore, we presume that the extent and pattern of the changes in the expiratory effort for increasing vocal intensity may vary according to the types of laryngeal lesions. To prove these hypotheses, we investigated the changes in expiratory effort for increments of the vocal intensity by measuring the expiratory lung pressure. The subjects included 10 each of normal controls, patients with Reinke's edema, and those with recurrent laryngeal nerve paralysis. For the normal controls, the increase in vocal intensity was achieved by slightly increasing the expiratory lung pressure. The patients with Reinke's edema showed a greater increase in expiratory lung pressure, as compared with the normal group. The patients with recurrent laryngeal nerve paralysis exhibited greater expiratory effort with extreme increases in airflow than normal group for louder phonation. It was concluded that the subjects who have phonatory disorders, in comparison with normal individuals, require a greater expiratory effort. This phonatory function test with an increase in voice intensity made the aerodynamic pathologic condition clearer.