The tear break-up time (BUT), Schirmer's I test (S-I) and slit lamp examination after rose Bengal staining (RBS) are simple tests for evaluation of keratoconjunctivitis sicca (KCS). Discrepancies, however, regarding the range of normal values and the specificity and sensitivity of these methods prompted us to reevaluate them in 81 primary Sjögren's syndrome patients (Ss) and 276 normal volunteers. In normal volunteers, BUT values ranged from 4 sec. to 32 sec. (means +/- SD: 13 +/- 6 sec.) and in primary Ss from 1 sec. to 15 sec. (means +/- SD: 7 +/- 3 sec.). Ninety five percent (95%) of the values from primary Ss patients were below 12 sec. Forty two percent (42%) of the values obtained from normal individuals fall within this range. Schirmer's I test values in normal individuals ranged from 0 mm/5 min. to 30 mm/5 min. (means +/- SD: 10 +/- 9 mm) and in primary Ss patients from 0 mm/5 min. to 30 mm/5 min. (means +/- SD: 4 +/- 7 mm.). Ninety five percent (95%) of the primary Ss patients' values were below 19 mm/5 min. Sixty eight percent (68%) of the normal individual values fall into this range. Rose Bengal staining values ranged in normals from 0 to 7 (means +/- SD: 1 +/- 1) and in primary Ss patients from 1 to 8 (means +/- SD: 5 +/- 2). Ninety five percent (95%) of the primary Ss patients' values were above 2. Only 7% of normal individual values fall into this range. From these data we conclude that rose Bengal staining is the best test for evaluation of keratoconjunctivitis sicca.