Age related changes in the activity of lysosomal enzymes have been studied in the cultured human retinal pigment epithelium cells collected from 26-85 year old donors. Among four such enzymes studied, activities of cathepsin D and beta-glucuronidase increased with the age of the donors while no notable change in activity of arylsulfatase B and alpha-mannosidase was observed. Kinetic parameters of beta-glucuronidase was measured in retinal pigment epithelium cells isolated from donors of different ages. Similar kinetic parameters for beta-glucuronidase at different ages suggest that the observed increase in the activity of the enzyme with age is not due to post-translational modification of the enzyme. Western blot analysis provides evidence for increased synthesis of beta-glucuronidase with aging. Relative proportions of glycosaminoglycans, the natural substrates of beta-glucuronidase and arylsulfatase B, in the retinal pigment epithelium altered with the age of the donors. A significant decrease of dermatan sulfate levels with aging correlates well with the observed increase in the level of beta-glucuronidase activity.