To fabricate a prosthesis which is functionally harmonized with the stomatognathic system, the interocclusal relationship must be reproduced as accurately as possible. This study investigated the influence of the occlusal contacts upon tooth displacement and clarified the optimal occlusal contacts for the prosthesis. The displacement paths of six maxillary left first molars of six adults in good general health were measured in this study. We gave each test tooth eight patterns of artificial occlusal contacts by attaching platinum foil on the occlusal surface. Subjects were asked to perform clenching at the intercuspal position (= ICP) with medium occlusal forces, and 3-dimensional tooth displacement paths were measured by the Type M-3 tooth displacement transducer. The following conclusions were obtained. 1. Using the Student's t-test for statistical analysis, it was suggested that the difference of the buccolingual location of occlusal contacts influenced the direction of the tooth displacement. 2. The tooth which had occlusal contact in the buccal cusp displaced in the mesio-buccal direction, so this may create a wide dental arch and a slight discrepancy was generated at the distal interproximal contact area of the tooth. 3. It was shown that the tooth which had occlusal contact in the buccal cusp rotated in the buccoapical direction in reverse to the natural tooth.