While it is clear that the majority of the world's population suffers some deterioration of hearing--especially at high frequencies--with the advance of age, it is equally clear that some individuals reach very old age with clinically normal hearing. It is often difficult to separate the biological changes of senility from the effects of auditory environmental changes, and of specific pathological changes associated with specific disease entities. A better understanding of the etiology of presbyacusis is needed. The first step towards this end is the recognition that not all hearing impairment in the aged is due to biological ageing. This is important because hearing loss due to the acceleration of biological and environmental effects (accelerated presbyacusis) may be preventable, while hearing loss due to biological ageing (presbyacusis) is not treatable. The second step is the realization that not all hearing impairment over age 65 is due to ageing. Hearing impairments that are rapidly progressive, profound, asymmetrical, or fluctuating, and those associated with a marked conductive element or severe dizziness might well be associated with specific ear disease (Nosoacusis) such as infection, otosclerosis, Menière's disease, or acoustic tumor. A full neuro-otological evaluation including ABR, CT scan, ENG and others should be done in any patient over 65 suspected of having a specific ear disease. The classification presented demonstrates the need to revise the criteria used in determining 'Presbyacusis Curves'. These provide a reference standard for normal hearing at any age or decade. There are too many variables in the averages obtained from different subjects to make those averages a dependable standard reference.