Nineteen guinea pigs of one month and 11 of 30 months were given high fat diet for 3 months to produce hyperlipidemia; 16 of them followed by 3 months' normal diet to resume blood lipid level; 27 for control. The results showed that: The serum cholesterol level of the experimental groups was markedly elevated (P < 0.01) with fatty degeneration of liver. Damages in OHC, IHC, cells of stria vascularis and few myelin sheaths of cochlear nerve were seen in all experimental animals, and the reduction of cochlear damages was not seen in those animals with blood lipid level resumed to normal. Auditory dysfunction was very marked as shown by ABR in the old animals with hyperlipidemia as compared with controls (P < 0.01).