The purpose of this study was to clarify the influence of an experimental palatal plate on the mandibular position during continuous [n] phonation and at the physiologic rest position. Twenty healthy dentulous volunteers (10 males and 10 females, mean age of 24.4 years) were investigated. Three kinds of experimental plate with a thickness of 3 mm, 5 mm, and 8 mm were fabricated and used for each subject. The mandibular position was recorded by a K7 kinesiograph during continuous [n] phonation and at the physiologic rest position under normal conditions and when the three kinds of plate with different thickness were worn separately. The results showed that the mean interocclusal dimensions during continuous [n] phonation were 0.5 mm vertically and 0.4 mm anteroposteriorly under the normal condition. After insertion of an experimental plate, the interocclusal distance increased a little, but the difference was not statistically significant between the normal condition and any of the three experimental conditions. No significant difference was found between the male and female groups. Furthermore, no significant difference in the interocclusal distance at the physiologic rest position was found between the above comparisons. Within the limitations of this study, we concluded that the mandibular position during continuous [n] phonation and at the physiologic rest position was not significantly influenced by the experimental plates.