The etiology and pathogenesis of lumbar disc herniation is not clearly proved although biochemical change, physical stress, genetic factor, autoimmune phenomenon and psychophysiologic phenomenon have been considered by many investigators. The most important one is a result of pathologic acceleration of normal aging of the tissue. The present study is aimed to investigate the changes of mucosubstances in normal aging and herniated disc which might have possible role on the disc herniation. The materials used in this study consisted of 123 cases of surgically removed herniated disc and 7 cases of normal control disc obtained from autopsy. Sections were cut and stained with periodic acid-schiff (P.A.S.)-alcian blue (pH 2.5) for the detection of neutral mucosubstances, alcian blue at pH 2.5 for nonsulfated acid mucosubstances, and alcian blue at pH 1.0 and Spicers diamine method (HID) for sulfated mucosubstances. The results were as follows. l. Of the 123 cases of lumbar disc herniation, there was a slight male preponderance over female with a ratio of 1.5:1.0. The most commonly affected level was L4-5 comprising 69 cases (56.1%), and up to three quarters of the patients the age was from 3rd to 5th decades in which it was rather evenly distributed. 2. The time interval between the appearance of symptoms and operation was less than 1 year in 77 cases (62.6%), in 32 cases (26.0%) being within 3 months. 3. Histochemical studies of the normal discs showed increase of neutral mucopolysaccharides with reduction of acid and sulfated mucopolysaccharides in the nucleus pulposus, and increase of all the mucosubstances in the annulus fibrosus by aging. 4. Histochemical studies of herniated disc showed an acceleration of the changes seen in normal changes. 5. Cartilaginous end plate formation was noted in 46,3% of herniated discs. The results obtained by the present investigation suggest that herniation of lumbar diosc is closely associated with accelerated or premature degeneration of the disc.