Using commercially available reagents we developed an enzyme-linked immunosorbent assay to measure lactoferrin in normal human tears. Tears obtained from 38 normal human subjects contained a mean lactoferrin content of 2.2 mg/ml (g/l). No differences in the mean level of lactoferrin were found when tears were collected by either Schirmer tear strips or by glass capillaries after short tear gas stimulation. Tear lactoferrin levels were not influenced by age or sex of the subjects investigated in this study. We found that lactoferrin represents approximately 25% by weight of the total tear proteins.