In this paper the so-called 'normal' or 'ideal' occlusal relationships are described in static centric as well as in dynamic, eccentric positions. However, difference is made between the different occlusal concepts. There is no real antagonism between the 'physiologic occlusal concept' in natural dentition and the 'therapeutic occlusal concept' on which the treatment should be based in restoring the occlusion. The different forms of occlusion and articulation found in the natural dentition are the expression of physiologic, biological variations. The rest position of the mandible is an unreliable reference point in occlusal rehabilitation. Moderate attrition in older patients should not be considered as pathologic and there is no indication for treatment in absence of functional pathology.