Occlusal splints have been widely used in dentistry for treatment and diagnosis of signs and symptoms related to dental occlusion. The autor studyed the effect of occlusal splint on masticatory movement of young adult men (mean age 23.8 yrs.). Who had worn. occlusal splint for 1 week. The result were as follows: 1. Lateral movement of the mandible during mastication could be increased after wearing occlusal splint for 1 week. 2. Vertical movement of the mandible during mastication was increased after wearing occlusal splint for 1 week. 3. Maximum opening velocity of the mandible during mastication was increased after wearing occlusal splint for 1 week. 4. Mandibular movement during mastication was more affected by chewing of hard foods than of soft foods following occlusal changes. 5. Steepness of the anterior guidance affected several aspects of masticatory movement. 6. Masticatory movement of the mandible became more regular after wearing occlusal splint for 1 week.