The enzymes α-galactosidase,β-galactosidase, β-hexosaminidase, β-glucuronidase, acid phosphatase and alkaline phosphatase were investigated in human tear fluid and serum. The activities of the acid hydrolases in tear fluid are higher than in serum. The pH activity distributions are similar in tears and serum for α-galactosidase, β-galactosidase and β-hexosaminidase, but are not the same in these fluids for acid phosphatase and β-glucuronidase. The origin of these enzymes is likely to be found in the lysosomes of the secretory cells in the lacrimal gland’s acini. Alkaline phosphatase is also present in tear fluid with equal activity and similar characteristics as in serum. The source of this enzyme probably is to be found in the epithelial cells of the lacrimal gland’s ducts.