An accurate measurement of tear production is clinically important in the diagnosis and monitoring of dry eye conditions. Re-examination of the results of Schirmer test indicated that the rate of tear secretion decreased with advancing age. Fluorophotometry revealed that the tear turnover rate also decreased with age. Then reappraisal was made on the clinical tests for dry eye syndrome. The non-invasive tear film breakup time (NIBUT) showed a reasonable level of accuracy with a cut-off value of 5 seconds (sensitivity 95.9% and specificity 90.8%). The concentration of lactoferrin showed an optimal level of accuracy with a cut-off value of 1.1 mg/ml (sensitivity 79.4% and specificity 78.3%). A study of the ocular surface area revealed that the decrease of ocular surface area was related to the values of NIBUT in normal subjects younger than 50 years of age. The present findings suggested that a combination of these clinical tests was needed for the diagnosis of dry eye syndrome.