To investigate the variation of the mandibular rest position according to time, the mandibular rest position was induced by combination of relaxation and swallowing method. The displacement of the incisal point was recorded with the pinpointed miniature lamp luminograph in three dimensions immediately, 30 seconds, and 60 seconds after induction of the mandibular rest position. The Results obtained were as follows 1. Intermaxillary vertical distance measured immediately after induction of mandibur rest position ranged from 1.0mm to 3.9mm And it varied irregularly with time, ranging from 0.1mm to 1.1mm Anteroposterior variance with time ranged irregularly from 0.2mm to 0.8mm 2. The mandibular rest position observed in the frontal plane varied with time to right or left direction, ranging from 0.2mm to 0.5mm from the centric occlusion 3. the mandibular rest position wos not placed definite position but varied spatially in certain range with time.