The effect of increasing the occlusal vertical dimension on the mandibular postural relation was studied for eight subjects. Interocclusal rest space measurements were made weekly for 1 month prior and subsequent to increasing the occlusal vertical dimension by 3.5 to 4.5 mm interincisally using luted acrylic resin, complete-arch, fixed partial dentures. Interocclusal rest space measurements were made at the clinical rest position, which was established by requesting the subjects to close in maximum intercuspation and immediately relax their mandible. Interocclusal rest space measurements were also made at the more open resting position when the subjects were repeatedly instructed to relax and lapse into a semi-hypnotic condition termed elaxed resting posture. Initial speech difficulties and muscle discomfort subsided after 1 to 2 weeks. Analysis of variance using repeated measures showed no significant difference in interocclusal rest space after increasing the occlusal vertical dimension for both clinical rest position and relaxed resting posture. A significant difference was found between clinical rest position and relaxed resting posture (P = .001), and no interaction was determined between clinical rest position, relaxed resting posture, and time.