In orthodontic view points, there were a few attempts to describe on the mandibular rest position with roentgenocephalometric studies for the persons with malocclusion. The purpose of the present study was to evaluate and interpret the difference in each of the Angle´s classification of the malocclusion. The author has selected 115 malocclusion patients of the both sexes as subjects, whose dental ages were from III A. Two lateral cephalometric head films were taken mandible at rest and with the teeth in occlusion utilizing the Broadbent-Bolton cephalometer. Their linear and angular measurements were made directly. The author obtained the following results: 1) The change in the incisal overbite was of -2.32~-3.36mm, and the overjet decreased similiarly in each class of the malocclusion. 2) The range of free-way space was of 1.97~3.56mm, and showed prominent in the Angle´s class III malocclusion. 3) In the rest position, the mandible showed backward displacement, and it was prominent in the Angle’’s class III malocclusion. 4) In the change of Ar-Gn, the class I and II showed more increase of distance-than the class III. 5) In the change of ∠SNL1L1´, the class III showed smaller angle than the class I and II. 6) There was no significant difference between the male and female in each class of the malocclusion.
