The present study was conducted to compare the spatial relationship of the condyles to their fossae in the centric occlusion and centric relation positions. Right and left TMJ radiographs were obtained on 40 young adults in the two positions. Direct measurments of the anterior, posterior, and superior spaces between the condyles and their fossae were made on the radiographs. Results were statistically analyzed; the following findings and conclusions were derived: (1) In the centric relation position, both condyles were placed more posteriorly and superiorly in their fossae than in the centric occlusion position. (2) In the centric occlusion position, both condyles were symmetrically placed in their fossae with equal spatial distances anteriorly and posteriorly. (3) Greater spatial differences existed between the centric occlusion and centric relation positions on the left side, which was the orbiting (balancing)side in most subjects. (4) Further studies are needed to develop a more physiologic approach for correctly relating the mandible to the maxillae when reconstructing the occlusion in both dentulous and edentulous patients.