Bilateral TMJ of 7 edentulous patients were studied by CT in two positions. One position was to make the complete dentures in intercuspal position (ICP) while the other one was to make the edentulous jaws in closed position. Two of them MRI examination was made. It is discovered that the condyles move backward and upward in the glenoid fossa. The displacement of the disc in edentulous closed position is less in comparison with ICP. It is proposed that loss of vertical dimension such as abrasion and loss of dentition may press the disc anteriorly as a result of condyle displacement which it is a causal factor of TMJDS.