BACKGROUND In esophageal and tracheoesophageal speakers, the neoglottis acts not only as the orifice of the digestive tract but also as the airway and the voice source. The opening and closing mechanism is thought to be essential for these functions. It is not known, however, whether there is any active muscular control of neoglottal opening and closing. Examinations have been carried out to find the physiological background of the opening and closing of the neoglottis. In this paper, we present our findings of the opening and closing mechanism of the neoglottis and discuss them with reviewing the previous studies. SUBJECTS AND METHODS Subjects were volunteer esophageal speakers. Neoglottal width, EMG of the inferior pharyngeal constrictor (IPC) and that of the geniohyoid muscle (GH) were recorded simultaneously during swallowing and air intake for esophageal speech. RESULTS At rest, the neoglottis was closed by the mucosal protrusion in the posterior wall of the pharyngoesophagus. During swallowing, the neoglottis was widely opened. Traction of the anterior pharyngeal wall anteriorly by the GH and reciprocal suppression of the IPC activity was thought to be the mechanism of the neoglottal opening in this case. However, such simple reciprocity was not observed during air intake, although transient opening of the neoglottis was commonly observed. The GH showed increased activity at neoglottal opening as it did during swallowing. The IPC was. on the other hand, continuously activated, and no significant suppression was observed. During air intake, the muscle is assumed to play a role in maintaining the shape and tension of the posterior mucosal protrusion which acts as a voice source in subsequent phonation. CONCLUSIONS The GH and the IPC were found to open and close the neoglottis, respectively. Their activities were not always clearly reciprocal in the various functions of the neoglottis.