The occlusion of the teeth has been said to be the basis for the science of den­ tistry. In spite of this, the subject of occlusion has been much talked about, but little has been done about it until recently. This paradoxical situation can be traced to the dental curriculum. In the average dental school the stu­ dent’s first contact with the subject of oc­ clusion comes at the time that he articu­ lates the teeth that he has carved so laboriously. Emphasis is placed on the ideal or normal interdigitation of the teeth. His next contact with the subject of occlusion comes in the complete denture department where the student is taught the articulation of artificial teeth and is given a fixed mechanical concept of functional occlusion. Again, the con­ cept that is presented to the student is the ideal situation. In many schools this has been the extent of the formal course work. With this meager background the neophyte practitioner is expected to be able to analyze critically his patients’ occlusions and to institute the correct treatment for the occlusal disharmonies which are detected. In recent years the dental schools have been made aware of this deficiency in the student’s background and have taken steps to remedy the situation. Also, an increased emphasis has been placed on this subject by dental societies throughout the nation. This awakening of interest has been brought about pri­ marily by two groups, the periodon­ tists and the occlusal reconstructionists. Through panel discussions at dental meetings, a unified concept of occlusion in its broadest aspect gradually is being achieved. The purpose of this paper is to define the characteristics of the various types of occlusion and to point out the varia­ tions that exist in the general population. Occlusion implies more than just how the teeth meet when the jaws are closed. Such a concept would be a static one and would be useless when applied to a living being. In order to be useful, a concept of occlusion must be dynamic or functional. Anderson1 has aptly said: